Breast conservation surgery for breast cancer at a regional medical center

BACKGROUND

This study examined trends in breast conservation surgery (BCS) at our hospital and factors associated with BCS.

METHODS

We retrospectively reviewed breast cancer surgeries in patients eligible for BCS (size <4 cm, N0, N1) from 1990 through 1996 (n = 634). We calculated the yearly prevalence of BCS and used multiple logistic regression (MLR) to determine tumor, patient, and surgeon factors associated with BCS.

RESULTS

BCS increased from 17% in 1990 to 41% in 1996. Women with T1a and T1b tumors were 3.8 and 2.0 times, respectively, as likely to have BCS compared with those who had T2 tumors. Other factors associated with BCS included nonpalpable tumors, age <50, Medicare, Medicaid, or self-pay patients, and women whose surgeons graduated since 1961, with odds ratios of 1.8, 1.9, 2.4, and 2.3, respectively.

CONCLUSION

Women with small, nonpalpable tumors, age <50, without private insurance, operated on by younger surgeons were more likely to receive BCS.

DRG reimbursement: geriatric hip fractures in the community hospital trauma center

BACKGROUND

The purpose of this paper was to determine whether Medicare reimbursement for hip fracture reaches cost in geriatric patients.

METHODS

We conducted a retrospective review using the hospital trauma registry. Demographics, operations, length of stay, clinical outcome, discharge disposition, hospital charges, and hospital costs were reviewed and compared with diagnosis-related group (DRG) reimbursement.

RESULTS

The study included 153 Medicare patients. Mortality was 3.9%, 71% were discharged to a nursing home or rehabilitation unit, and 25% went directly home. DRG reimbursement constituted 58% of charges. Compared with costs, the DRG amount represented a mean loss of nearly $1,000 per patient.

CONCLUSIONS

DRG reimbursement undercompensates the community hospital trauma center for treating a common malady among the geriatric population. A population shift toward the elderly, decreasing Medicare remuneration, and the advance of managed care will make correct identification and control of costs extremely important for the hospital caring for hip fractures in the geriatric population.

Succinyl-CoA:3-ketoacid coenzyme A transferase (SCOT): development of an antibody to human SCOT and diagnostic use in hereditary SCOT deficiency

Succinyl-CoA:3-ketoacid CoA transferase (SCOT) is a key enzyme for ketone body utilization. Hereditary SCOT deficiency in humans (McKusick catalogue number 245050) is characterized by intermittent ketoacidotic attacks and permanent hyperketonemia. Since previously-available antibody to rat SCOT did not crossreact with human SCOT, we developed an antibody against recombinant human SCOT expressed in a bacterial system. The recombinant SCOT was insoluble except under denaturing conditions. Antibody raised to this polypeptide recognized denatured SCOT and proved useful for immunoblot analysis. On immunoblots, SCOT was easily detectable in control fibroblasts and lymphocytes but was detected neither in fibroblast extracts from four SCOT-deficient patients, nor in lymphocytes from two SCOT-deficient patients. These data indicate that immunoblot analysis is useful for diagnosis of SCOT deficiency in combination with enzyme assay.

Clinicopathologic factors and patient perceptions associated with surgical breast-conserving treatment

BACKGROUND

Clinical studies have shown equivalent survival rates between breast-conserving surgery (BCS) and mastectomy in early breast cancer; however, rates for BCS remain low. The purpose of this study was to determine (a) the prevalence of BCS in a regional medical center, (b) clinicopathologic factors associated with BCS, and (c) patient perceptions of the treatment decision-making process.

METHODS

We retrospectively reviewed 251 consecutive breast cancer cases during January 1990-December 1991; 77 patients were ineligible for BCS because of unfavorable pathology. We then interviewed 118 of the 160 women available for interview.

RESULTS

BCS was performed in 31 of the eligible patients (18%). Multivariate analysis revealed that tumor size < 10 mm (p = 0.03) was the only significant predictive variable for BCS. Patient interviews revealed that 93% said their surgeon was the primary source of information regarding treatment options. Among 69% of the women whose surgeons reportedly recommended a particular option, 89% recommended mastectomy with 93% compliance, and 11% recommended BCS with 89% compliance. The BCS group more often obtained a second opinion (p = 0.04) and 60% said they made the decision themselves compared with only 37% of the mastectomy group (p = 0.05).

CONCLUSION

Limiting BCS to women whose tumor size is < 10 mm is too restrictive; this excludes a large number of women who are clinically eligible for BCS. The surgical decision-making process for early-stage breast cancer is very much surgeon-driven, with a high degree of patient compliance.

Purification and characterization of D-beta-hydroxybutyrate dehydrogenase expressed in Escherichia coli

D-beta-Hydroxybutyrate dehydrogenase (BDH), a lipid-requiring enzyme, has been cloned into pUC18, expressed in Escherichia coli, and purified to homogeneity. The apoenzyme, i.e., the enzyme devoid of phospholipid, has no activity, but can be activated by phospholipid to a specific activity of 129 mumol/(min.mg). The functional properties of the enzyme expressed in E. coli were compared with the enzyme purified from rat liver. The specific activities, kinetic parameters, and phospholipid activation profiles were virtually identical. These results indicate that the expression of the enzyme in E. coli is a viable method for producing active functional BDH and should allow for the production of specifically altered BDH molecules.

The baroreceptor mechanism for controlling renin secretion: effect of calcium channel blockers

Renin secretion is inversely related to afferent arteriolar transmural pressure, or to some function of it such as stretch (the baroreceptor mechanism). It has been suggested that increased pressure depolarizes the renin-secreting juxtaglomerular cells, and that increased Ca influx through voltage-operated Ca channels mediates the inhibitory effect on renin secretion. If true, then Ca channel blockers should antagonize the inhibitory effect of increased pressure on renin secretion. To test this prediction, isolated rat kidneys were perfused with an oxygenated physiological salt solution in a single-pass system. Perfusate flow rate and renin concentration in the venous effluent were measured and their product, the renin secretory rate (RSR), was calculated. During the control period, increasing renal perfusion pressure (RPP) from 100 to 120 mm Hg decreased RSR to 42 +/- 5% of the control value. This inhibitory effect of increased RPP was blunted by 1 microM nifedipine, nearly blocked by 5 microM verapamil and completely blocked by 50 microM diltiazem. Inasmuch as nifedipine, verapamil and diltiazem are Ca channel blockers and because all three have been shown previously to block the inhibitory effect of depolarization on RSR, these results are consistent with the hypothesis that a depolarization-induced influx of Ca mediates the inhibitory effect of increased RPP on RSR.

BAY K 8644 inhibits renin secretion in isolated perfused rat kidneys

There are only a few previous reports of the renal effects of the Ca channel agonist BAY K 8644, and the renin secretory effects in particular are unclear. In the present experiments, isolated rat kidneys were perfused at 120 and 100 mm Hg before and after adding BAY K 8644 to the perfusate (0.05 microM final concentration), and perfusate flow rate, glomerular filtration rate (GFR), urine flow, Na excretion, and renin secretory rate were measured. BAY K 8644 increased renal vascular resistance, as evidence by decreases in perfusate flow and GFR at constant perfusion pressure, and decreased urine flow and Na excretion. Renin secretory rates were 51 +/- 4 versus 23 +/- 3 ng A I hr-1 min-1 at 120 mm Hg (p < 0.01), and 184 +/- 54 versus 38 +/- 14 ng A I hr-1 min-1 at 100 mm Hg (p < 0.01), in the absence versus the presence of BAY K 8644, respectively. Therefore, BAY K 8644 inhibits renin secretion at constant perfusion pressure and blunts the stimulatory effect on renin secretion of decreases in renal perfusion pressure. Collectively, these observations add to the growing evidence that the renin secreting juxtaglomerular cells have voltage-operated Ca channels, that depolarization-induced Ca influx inhibits renin secretion, and that Ca is an inhibitory second messenger in the renin secretory process.

Streptozotocin-induced renal hemodynamic changes in isogenic Lewis rats: a kidney transplant study

Streptozotocin (STZ)-induced diabetes mellitus is associated with decreased renal clearances of inulin and p-aminohippurate (PAH). The present experiments were designed to determine whether STZ-induced renal hemodynamic changes are due to the drug per se, rather than to the diabetic state that it induces. Isogenic Lewis rats with native right and transplanted left kidneys were studied. In one group, kidney donors received 50 mg STZ/kg body wt on day 1 and transplantation was performed on day 4 (untreated recipients). On day 29, the inulin and PAH clearances of these nondiabetic recipients were, respectively, 0.94 +/- 0.04 and 2.58 +/- 0.11 ml.min-1 x g-1 for the transplanted left kidney (previously exposed to STZ) and 0.95 +/- 0.07 and 2.54 +/- 0.14 ml.min-1 x g-1 for the native right kidney (never exposed to STZ). In another group, recipients received STZ on day 1 and transplantation was performed on day 4 (untreated donors). On day 29, the inulin and PAH clearances of these diabetic recipients were, respectively, 0.62 +/- 0.04 and 1.46 +/- 0.11 ml.min-1 x g-1 for the transplanted left kidney (never exposed to STZ) and 0.61 +/- 0.05 and 1.42 +/- 0.08 ml.min-1 x g-1 for the native right kidney (previously exposed to STZ). We conclude that the diabetic state, rather than STZ, is responsible for the decreased renal clearances of inulin and PAH in this experimental model.

Primary structure of rat liver D-beta-hydroxybutyrate dehydrogenase from cDNA and protein analyses: a short-chain alcohol dehydrogenase

The amino acid sequence of D-beta-hydroxybutyrate dehydrogenase (BDH), a phosphatidyl-choline-dependent enzyme, has been determined for the enzyme from rat liver by a combination of nucleotide sequencing of cDNA clones and amino acid sequencing of the purified protein. This represents the first report of the primary structure of this enzyme. The largest clone contained 1435 base pairs and encoded the entire amino acid sequence of mature BDH and the leader peptide of precursor BDH. Hybridization of poly(A+) rat liver mRNA revealed two bands with estimated sizes of 3.2 and 1.7 kb. A computer-based comparison of the amino acid sequence of BDH with other reported sequences reveals a homology with the superfamily of short-chain alcohol dehydrogenases, which are distinct from the classical zinc-dependent alcohol dehydrogenases. This protein family, initially discerned from Drosophila alcohol dehydrogenase and bacterial ribitol dehydrogenase, is now known to include at least 20 enzymes catalyzing oxidations of distinct substrates.

Cloning and expression of a functional rat liver D-beta-hydroxybutyrate dehydrogenase-beta-galactosidase fusion protein in Escherichia coli

A rat liver bacteriophage lambda expression library was probed using polyclonal antibodies raised to purified rat liver D-beta-hydroxybutyrate dehydrogenase (BDH). A clone was selected that contained a 1.2-kb insert. The insert placed in an expression plasmid was utilized to transform Escherichia coli. These cells were shown to possess phosphatidylcholine-dependent BDH activity. Cells transformed with only the plasmid had no detectable BDH activity in the presence of phosphatidylcholine. The expressed activity in E. coli could be inhibited in a dose-dependent manner by BDH antiserum.

High osmolality-low pH flush solutions improve renal transplant function in rats

Although transplanting rat kidneys is an established microsurgical technique, inulin clearance is abnormally low, due to rejection and/or warm ischemia-induced damage. In the present studies, rejection was avoided by using inbred Brown Norway rats as donors and recipients. Donor kidneys were flushed with ice-cold solutions of various composition (saline, saline + 200 or 400 mM mannitol) and pHs (5.7, 6.4, and 7.4), and the kidneys were kept cold during transplantation into unilaterally nephrectomized recipients. Renal function was assessed by clearance techniques 1 week later. In control rats, with both native kidneys intact, the ratio of inulin clearance, left kidney to right kidney, was 0.99 +/- 0.02. In rats with a native right kidney and a transplanted left kidney that had been flushed with saline, the ratio was considerably lower (0.46 +/- 0.09). Adding 200 mM mannitol to the saline flush solution increased the ratio (0.89 +/- 0.09). In comparison, adding 200 mM mannitol and 5 mM phosphate buffer at pH 7.4 resulted in a somewhat lower ratio (0.80 +/- 0.09), whereas adding 200 mM mannitol and 5 mM phosphate buffer at pH 5.7 resulted in a higher ratio, one that was indistinguishable from control (0.97 +/- 0.09). Thus, in this latter group, the inulin clearances of the transplanted kidneys were identical to those of the contralateral native kidneys.

Patient awareness of health precautions after splenectomy

Sepsis after splenectomy is a lifelong risk, and patients who have had splenectomy should be educated about this risk. This study examines patient knowledge after splenectomy. We reviewed hospital records of 118 patients who had splenectomies performed between 1982 and 1988 at New Hanover Memorial Hospital. Twenty-four patients have died since their surgery; one death was suspected to be due to postsplenectomy sepsis. Of the 89 patients alive and eligible for follow-up, we were able to query 63. Only 16% were aware of any health precautions. After prompting, patient awareness improved to 40%. We also surveyed 11 of the 14 surgeons who performed the splenectomies. They indicated that they always discuss with their patients the immunologic consequences of spleen removal and the increased risks of infection, although they do not always recommend pneumococcal vaccine. We conclude that splenectomy patients have a low level of knowledge about postsplenectomy infection risks and precautions. We developed an educational pamphlet to aid the surgeon in patient education.

Community hospital carotid endarterectomy in patients over age 75

We compared the prevalence of stroke and death in 133 patients aged 75 and older in whom 170 carotid endarterectomies were performed with that in 501 patients less than age 75 in whom 640 carotid endarterectomies were performed. There were three strokes (2%) in patients aged 75 and older and nine strokes (1%) in younger patients (p = 0.7). There were 8 deaths (5%) in patients aged 75 and older and 14 deaths (2%) in younger patients (p = 0.1). After controlling for the possible confounding effects of diabetes, prior stroke, history of angina, prior carotid artery disease, previous vascular surgery, history of myocardial infarction, preoperative hypertension requiring medication, and female gender, a logistic regression model showed that patients aged 75 and older were no more likely to have a stroke or death than patients under age 75. We conclude that age alone is not a contraindication to the safe performance of carotid endarterectomy in the community hospital.

Comparison of D-beta-hydroxybutyrate dehydrogenase from rat liver and brain mitochondria

The properties of D-beta-hydroxybutyrate dehydrogenase (BDH) from rat liver and brain mitochondria were compared to determine if isozymes of this enzyme exist in these tissues. The BDHs from these tissues behaved similarly during the purification process. The enzymes were indistinguishable by sodium dodecyl sulfate-polyacrylamide or acid-urea-polyacrylamide gel electrophoresis and they had identical isoelectric points. The BDHs from rat liver and brain were also quite similar in functional parameters determined by kinetic analysis and phospholipid activation of apo-BDH (i.e., the lipid-free enzyme). Antiserum against rat liver BDH inhibited both enzymes to an equivalent extent in a titration assay. The enzymes had similar patterns of peptide mapping by partial digestion with Staphylococcus aureus V8 protease, followed by immunoblotting using antiserum against the liver enzyme. These results suggest that the BDHs in rat liver and brain are very similar and possibly identical.

The use of amphipathic maleimides to study membrane-associated proteins

A series of amphiphilic polymethlyenecarboxymaleimides has been synthesized for use as sulfhydryl reagents applicable to membrane proteins. Physical properties of the compounds which are relevant to their proposed mode of action have been determined. By comparing rates of reaction in aqueous and aprotic solvents, the compounds have been shown to react exclusively with the thiolate ion. The effects of the reagents on three membrane-associated proteins are reported, and in two cases a comparative study has been made of the effects on the proteins in the absence of membranes. A mechanism is proposed whereby the reagents are anchored at the lipid/water interface by the negatively charged carboxyl group, thus sitting the reactive maleimide in a plane whose depth is defined by the length of the reagent. Supporting evidence for this model is provided by the inability of the reagents to traverse membranes, and variation of their inhibitory potency with chain length when the proteins are embedded in the membrane, but not when extracted into solution. As examples of general use of the reagents to probe sulfhydryl groups in membrane proteins, the reagents have been used to (a) determine the depths in the membrane at which two populations of sulfhydryl groups occur in the mitochondrial phosphate transporter; (b) locate a single sulfhydryl associated with the active site of D-beta-hydroxybutyrate dehydrogenase in the inner mitochondrial membrane; (c) examine sulfhydryl groups in the D-3-glyceraldehyde phosphate dehydrogenase associated with the human red blood cell membrane.

Regulation of succinyl coenzyme A:acetoacetyl coenzyme A transferase in rat hepatoma cell lines

The regulation of succinyl-CoA:acetoacetyl-CoA transferase (CoA transferase) has been studied in 8 rat hepatoma cell lines. Compared with normal rat hepatocytes, which have almost nondetectable activity of the enzyme, the hepatoma cell lines have a wide range of expression of CoA transferase activity, from as low as 45 nmol/min/mg to as high as 960 nmol/min/mg. Western blotting showed that the different levels of CoA transferase activity were due to differing amounts of the enzyme in the cells. This was further attributed to the varying amounts of the enzyme synthesized in the cells as monitored by L-[35S]methionine labeling followed by immunoprecipitation. To study further the differential expression of CoA transferase in the hepatoma cell lines, the relative quantity of functional CoA-transferase mRNA in the cells was measured by in vitro translation. The results showed that the levels of functional CoA transferase mRNA detected were consistent with the differences in the enzyme activity in the cells. Since CoA transferase is the key enzyme responsible for the utilization of ketone bodies as an alternative energy source, the expression of CoA transferase in hepatoma cells may play a role in energy production.

Purification of D-beta-hydroxybutyrate dehydrogenase from rat brain

D-beta-Hydroxybutyrate dehydrogenase (BDH), a lipid-requiring enzyme, has been purified to homogeneity from rat brain using a new improved method. The purified rat brain BDH has a subunit molecular mass of 31 kilodaltons on sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The apoenzyme, i.e., the enzyme devoid of phospholipid, has no activity, but can be activated by phospholipid to a specific activity of 125 mumol/(min.mg). This is 625-fold greater than the activity in the mitochondrial fraction. The new purification procedure involves chromatography using a quaternary amine Sepharose resin followed by a sulphonate Sepharose resin, and eliminates the need for glass bead adsorption chromatography.

The role of adenosine in HgCl2-induced acute renal failure in rats

It has been proposed that adenosine mediates the renal hemodynamic changes in acute renal failure (ARF) and that these changes are pathogenic in reducing glomerular filtration rate. Consistently, adenosine-receptor antagonists such as theophylline have been shown to have protective effects in several experimental models of ARF. The present experiments were designed to explore the potential role of adenosine in HgCl2-induced ARF in rats. In isolated perfused rat kidneys, HgCl2 increased adenosine production and induced a concentration-dependent vasoconstriction. However, the vasoconstriction was unrelated to adenosine production and was not antagonized by theophylline. During the initiation phase of HgCl2-induced ARF in intact rats (first 4 h after injection), theophylline failed to reverse the reduction in inulin clearance, and this failure could not be attributed to a loss of vascular responsiveness to adenosine, since N6-cyclohexyladenosine, a receptor agonist, produced a further reduction in inulin clearance. Furthermore, theophylline actually had deleterious effects during the maintenance phase of HgCl2-induced ARF in intact unanesthetized rats, as evidenced by higher mean serum creatinine values in theophylline-injected rather than in saline-injected rats, on both the second and third days after HgCl2 injection. Therefore HgCl2 acutely increases renal adenosine production, but increased adenosine does not mediate acute HgCl2-induced renal vasoconstriction, and adenosine-receptor antagonism does not have protective effects during the initiation or the maintenance phases of HgCl2-induced ARF in rats. These results provide no support for the hypothesis that increased adenosine mediates the hemodynamic changes in HgCl2-induced ARF.

Kidney transplants in cyclosporine-treated Sprague-Dawley rats

Previous studies by others have shown that transplanted rat kidneys have abnormally low clearances of paraaminohippuric acid, inulin, and creatinine, due to rejection and/or to warm-ischemia-induced injury. In the present studies, randomly bred Sprague-Dawley rats were used as donors and recipients. The left kidneys of recipients were removed, and the right kidneys were left intact. Donor kidneys were flushed with an ice-cold hypertonic solution (150 mM NaCl, 200 mM mannitol, pH 6.4), and the kidneys were kept cold during surgery. Renal function was assessed 1 week later. The left transplanted kidneys in untreated recipients exhibited morphologic evidence of rejection, and the clearances of PAH and inulin were approximately 50% of those of the right native kidneys. CsA-treated rats did not reject the transplants, and the PAH and inulin clearances of the left transplanted kidneys were identical to those of the right native kidneys. Untreated and CsA-treated rats with both native kidneys intact served as controls. The amount of CsA given during the 7-day period produced no measurable change in renal function. This is the first demonstration of virtually normal hemodynamics in transplanted rat kidneys when randomly bred animals are used as donors and recipients. Moreover, the results indicate that if both rejection and warm ischemia are avoided, the presence of a functioning native kidney does not have a detrimental effect on the function of a transplanted kidney.

Developmental regulation of D-beta-hydroxybutyrate dehydrogenase in rat liver and brain

The activities of ketone-metabolizing enzymes in rat brain increase 3- to 5-fold during the suckling period before decreasing to the adult level after weaning. We have observed that a similar developmental pattern also exists for D-beta-hydroxybutyrate dehydrogenase (BDH) in rat liver. Utilizing antibodies prepared against the purified protein we determined that the changes in BDH activities in both brain and liver are due to changes in the amount of BDH in the mitochondria. In vitro translations of isolated RNA followed by immunoprecipitation revealed that the increase in BDH activity and content was correlated with an increase in the level of functional BDH-mRNA in both liver and brain.

Isolation of a cDNA encoding functional Drosophila alcohol dehydrogenase in Escherichia coli and purification of the bacterially produced enzyme

Because of the severe limitations on growing large quantities of Drosophila affinidisjuncta in the laboratory, direct purification of alcohol dehydrogenase (ADH) from this species has proven impossible. As an alternative source of this enzyme, a cDNA encoding functional ADH was isolated from a newly constructed cDNA library made from larval poly(A)-containing RNA. The cDNA was recovered by virtue of its hybridization to a previously isolated genomic ADH gene. Nucleotide sequence analysis confirmed the identity of the newly isolated cDNA. When the cDNA was inserted in the proper orientation downstream of the lac promoter on the vector pUC8, the cDNA directed the synthesis of functional ADH by the bacterial host. The bacterially produced enzyme was purified to homogeneity and used to elicit polyclonal antibodies in rabbits. The purified ADH has identical apparent subunit molecular weight to that of authentic ADH in larval fly extracts as determined by immunoblotting. Further, comparisons of the kinetic parameters of the bacterially produced enzyme and ADH activity in larval fly extracts indicate similar substrate preferences, pH dependencies, and Km values for 2-propanol and NAD. These results show that expression of a cDNA in Escherichia coli is a valid strategy for isolation of an ADH that would otherwise be difficult or impossible to purify.

Regulation of D-beta-hydroxybutyrate dehydrogenase in rat hepatoma cell lines

Quantitation of D-beta-hydroxybutyrate dehydrogenase (BDH) in normal rat hepatocytes was compared with that in two rat hepatoma cell lines, H4-II-EC3 and RLT-3C. BDH activity in normal rat hepatocyte mitochondria was 321 nmol/min/mg, which was greatly reduced to 10.7 nmol/min/mg and 1.7 nmol/min/mg in H4-II-EC3 and RLT-3C cell mitochondria, respectively. The cell growth rate and L-[35S]methionine incorporation rate showed that RLT-3C cells had the highest growth rate (32.4-h doubling time) and the fastest protein biosynthesis rate (2.65 x 10(5) cpm/min/10(6) cells). The H4-II-EC3 cell line grew more slowly (48.5-h doubling time) and had lower protein biosynthesis rate (1.46 x 10(5) cpm/min/10(6) cells). The protein synthesis rate in hepatocytes was 1.25 x 10(5) cpm/min/10(6) cells. These results suggest that there is a reciprocal correlation between BDH activity and cell growth and protein synthesis rates. Immunochemical quantitation of BDH showed the amount of BDH in H4-II-EC3 and RLT-3C cells was about 4.8 and 0.5% of that in normal rat hepatocytes, respectively. Quantitation of BDH by biosynthesis indicated that BDH content in H4-II-EC3 cells and RLT-3C cells was 9.3 and 4.0% of that of normal hepatocytes, respectively. Precursor BDH synthesized by in vitro translation primed with RNA of H4-II-EC3 cells or RLT-3C cells was 3.0 and 1.1% of that translated from normal rat hepatocyte RNA. These results suggest that the decrease in BDH content in hepatoma cells results from a decrease in functional BDH-mRNA. The coupling of a decrease in BDH activity with an increase in activity of succinyl-CoA: acetoacetyl-CoA transferase in hepatoma cells may play a role in generating additional energy required for the rapid growth of tumor cells.

Mechanism of adenosine receptor-induced renal vasoconstriction in rats

Adenosine analogues selective for the A1 subclass of adenosine receptors, such as N6-cyclohexyladenosine (CHA), induce vasoconstriction in the isolated rat kidney perfused at constant flow. Presumably, the vasoconstriction is mediated by increased Ca2+ concentration in renal vascular smooth muscle cells, but the mechanism by which A1 adenosine receptor occupation leads to increased Ca2+ is unknown. In the present experiments, the isolated, perfused rat kidney vasoconstricted in response to CHA, to K depolarization, and to BAY K 8644 (a Ca2+ channel agonist). All of these responses were completely blocked by methoxyverapamil, which suggests that CHA, like K depolarization and BAY K 8644, induces renal vasoconstriction by increasing Ca2+ influx through potential operated Ca2+ channels. The mechanism of action of CHA was different, however, in that pertussis toxin treatment blocked the response to CHA without affecting the responses to K depolarization or to BAY K 8644. Therefore, a pertussis toxin-sensitive step must intervene between occupation of A1 adenosine receptors on renal vascular smooth muscle cells and increased Ca2+ influx through potential-operated Ca2+ channels.

Renal effects of SK&F 82526 in anesthetized rats

Dopamine affects renal hemodynamics, renal tubular functions, and the secretion of renin. We have studied the renal effects of SK&F 82526 (an agonist which is selective for the DA1 subclass of dopamine receptors) in anesthetized rats. Infused intravenously at 0.005 mumol/min/kg, this drug increased renal plasma flow and the clearances of PAH and insulin, effects which are consistent with decreased renovascular resistance. Concomitantly, urine flow and K excretion increased, and Na excretion tended to increase. All these effects of SK&F 82526 were antagonized by intravenous metoclopramide (1 mumol/min/kg). Despite its diuretic effect and despite its lack of effect on arterial blood pressure, SK&F 82526 increased arterial plasma renin concentration, suggesting a stimulatory effect on renin secretory rate. Taken together, our results demonstrate that the renal effects of SK&F 82526 mimic those of dopamine.

Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides is a reliable internal standard for radiation-inactivation studies of membranes in the frozen state

The target size of four soluble enzymes (beta-galactosidase, pyruvate kinase, alcohol dehydrogenase, and glucose-6-phosphate dehydrogenase) in the presence or absence of subcellular membrane fractions has been determined by the radiation-inactivation method using samples in the frozen state. For each of the four enzymes, full activity was recovered after freezing and thawing in the absence of radiation. We found minimal (less than 20%) binding of the enzymes to either submitochondrial vesicles or sarcoplasmic reticulum vesicles. Under the conditions tested, beta-galactosidase, pyruvate kinase, and alcohol dehydrogenase exhibited target sizes which varied according to the experimental conditions, i.e., the buffer selected and also the presence or absence of membrane preparations. For these tetrameric enzymes, the target sizes were generally comparable to either a monomer or a dimer. By contrast, the target size of glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides was found to be essentially invariant when frozen in a variety of buffers and in the presence or absence of either cryoprotectant (sucrose or glycerol) or different membrane preparations. The target size from 19 separate determinations gave an average value of 104 +/- 16 kDa, which is comparable to the molecular weight of the enzyme (104 kDa). We conclude that glucose-6-phosphate dehydrogenase from L. mesenteroides is a reliable internal standard for radiation-inactivation studies of membrane preparations in the frozen state.

Interaction of liver microsomal cytochrome P-450 and NADPH-cytochrome P-450 reductase in the presence and absence of lipid

Phospholipid has been reported to be necessary for optimal catalytic activity of a number of mammalian cytochrome P-450 (P-450) systems. We also confirm that a number of individual phospholipids and mixtures, used as soluble monomers or phospholipid vesicles, show activation of 7-ethoxycoumarin O-deethylase activity by an enzyme system composed of rat liver microsomal P-450PB-B and NADPH-P-450 reductase. However, by preincubating a mixture of P-450 and NADPH-P-450 reductase at high concentrations, optimal activity can be obtained in the absence of phospholipid. The catalytic activity of the complex formed is concentration dependent in the absence of lipid or in the presence of soluble lipid. The activity in phospholipid vesicles is optimal and concentration independent. The apparent Km for NADPH-P-450 reductase in P-450-dependent oxidation systems is lowered severalfold in the presence of phospholipid. The apparent Km for the P-450 substrate, 7-ethoxycoumarin, and the temperature dependence of 7-ethoxycoumarin O-deethylase activity were unaffected by the addition of phospholipid to a preformed complex of P-450PB-B and NADPH-P-450 reductase. The effect of lipid on a number of other P-450 isozymes was also examined and in no case did lipid enhance the catalytic activity of the preformed complex. These results lead to the conclusion that the major effect of phospholipids in P-450-based enzyme systems is the facilitation of an active P-450:NADPH-P-450 reductase complex. This is the first report that maximum P-450 supported monooxygenase activity can be obtained in the absence of phospholipid.

The effect of denervation diuresis on the severity of glycerol-induced acute renal failure in rats

The results of several previous studies suggest that high urine flow rate has a protective effect in several models of experimentally induced acute renal failure. However, the methods employed to alter urine flow precluded a paired experimental design, left kidney vs. right kidney in the same experimental animal. The purpose of the present studies was to determine whether the unilateral diuresis that results from renal denervation has a protective effect on that kidney in glycerol-induced acute renal failure. Eight groups of rats were studied. The left kidneys of all were either denervated or sham-denervated; 3 to 5 days later, rats were injected with either 150 mM NaCl (controls) or glycerol; then either 3 or 24 hr after injection, renal function was measured in acute experiments. In saline-injected rats, the inulin clearances of right and left kidneys were virtually identical, whether the left kidney was denervated or not; however, in rats with denervated left kidneys, left kidney urine flow exceeded that of the right kidney whereas the opposite was true in rats with sham-denervated left kidneys. In contrast with saline-injected rats, there were highly significant differences in inulin clearances of right and left kidneys in glycerol-injected rats at both 3 and 24 hr after injection; left kidney inulin clearance exceeded that of the right in rats with denervated left kidneys, whereas right kidney inulin clearance exceeded that of the left in rats with sham-denervated left kidneys. Since the kidney with the higher urine flow had the higher inulin clearance at 3 and 24 hr after glycerol, whether or not the kidney was denervated, these results suggest that urine flow per se has a protective effect in glycerol-induced acute renal failure in rats.

Influence of diabetes on rat liver mitochondria: decreased unsaturation of phospholipid and D-beta-hydroxybutyrate dehydrogenase activity

Liver mitochondria and submitochondrial vesicles have been prepared from rats made diabetic by treatment with streptozotocin (diabetic membranes). The membranes were characterized in terms of phospholipid and fatty acid composition, electron transport functions, and D-beta-hydroxybutyrate dehydrogenase activity and compared with mitochondria and submitochondrial vesicles prepared from control animals (control membranes). No change in the phospholipid composition (44% lecithin, 35% phosphatidylethanolamine, and 21% diphosphatidylglycerol) was found, but a marked alteration in fatty acid composition of both the total phospholipid and lecithin occurred within 3 weeks after streptozotozin treatment and persisted thereafter. In lecithin, the 18:1/18:0 ratio decreases approximately 33% and the 20:4/18:2 ratio decreases approximately 55%. D-beta-hydroxybutyrate dehydrogenase is a lipid-requiring enzyme which has a specific requirement of lecithin for function. In diabetic membranes, there is a progressive decrease in D-beta-hydroxybutyrate dehydrogenase activity with time after streptozotocin treatment to about 40% of control value at 15 weeks. In contrast, succinate oxidase and succinate- or NADH-cytochrome c reductase activities remain essentially unaltered. Further, the Arrhenius plot characteristics differ for D-beta-hydroxybutyrate dehydrogenase in diabetic membranes as compared with control membranes, in that the break point of the biphasic plot increases from 20 +/- 1 degree C in controls to 29 +/- 1 degree C in samples from diabetic animals. The change occurs about 3 weeks after streptozotocin treatment and is correlatable with the increased saturation of the fatty acid moiety of the phospholipids. The observed changes in D-beta-hydroxybutyrate dehydrogenase function and phospholipid composition were prevented by administration of insulin to the diabetic animals and are therefore referable to insulin insufficiency.

Basis for decreased D-beta-hydroxybutyrate dehydrogenase activity in liver mitochondria from diabetic rats

Liver mitochondria from rats made diabetic with streptozotocin have a reduced level of D-beta-hydroxybutyrate dehydrogenase (BDH) activity and decreased ratios of oleic/stearic and arachidonic/linoleic acids in the phospholipids of the mitochondrial membrane. This altered activity and lipid environment result from insulin deprivation since maintenance of the diabetic rats on insulin leads to normal characteristics (J.C. Vidal, J.O. McIntyre, P.F. Churchill, and S. Fleischer (1983) Arch. Biochem, Biophys. 224, 643-658). In the present study, the basis for the reduced enzymatic activity of this lipid-requiring enzyme was analyzed using three approaches: (i) Purified D-beta-hydroxybutyrate, dehydrogenase was inserted into membranes from mitochondria, submitochondrial vesicles, and mitochondrial lipids extracted therefrom. The activation was the same and optimal irrespective of whether the preparations were derived from normal or diabetic rat liver. Therefore, the decreased activity does not appear to be referable to an altered lipid composition. (ii) BDH activity can be released from the mitochondria by phospholipase A2 digestion. The released activity was proportional to the endogenous activity in the submitochondrial vesicles from normal and diabetic membranes. (iii) The BDH activity in submitochondrial vesicles was titrated by inhibition with specific antiserum. Less enzyme was found in mitochondria from diabetic rats as compared with those from normal animals. Hence, the lowered enzymatic activity is due to decreased enzyme in the mitochondrial inner membrane and not to the modified lipid environment.

Renal effects of methoxyverapamil in anesthetized rats

The purpose of these experiments was to determine the renal effects of methoxyverapamil (D-600). Three groups of rats were anesthetized with sodium pentobarbital and given 0, 0.85 or 1.69 nmol/min of methoxyverapamil i.v. Increases in urine flow and Na, K and Ca excretory rates occurred, in an apparently dose-dependent manner. Plasma Na and arterial renin concentration decreased at both doses and, at the higher dose, mean arterial blood pressure and effective renal plasma flow decreased while plasma K increased. Plasma Ca, glomerular filtration rate, filtration fraction and total renal plasma flow were not affected. The findings that methoxyverapamil increased urine flow and electrolyte excretion without changing glomerular filtration rate are consistent with the hypothesis that methoxyverapamil acts directly on tubular reabsorptive mechanisms. These effects, and the effect on plasma renin concentration, could contribute to the beneficial effects of this and other Ca entry antagonists in the treatment of hypertension.

Target size of D-beta-hydroxybutyrate dehydrogenase. Functional and structural molecular weight based on radiation inactivation

D-beta-Hydroxybutyrate dehydrogenase is a lipid-requiring enzyme which is localized on the inner face of the mitochondrial inner membrane. The apoenzyme has been purified to homogeneity from beef heart; it is devoid of lipid and inactive. It can be functionally reconstituted with lecithin or phospholipid mixtures containing lecithin. The active form of the enzyme is the enzyme-phospholipid complex. Classical target analysis of radiation-inactivation data has now been used to determine the molecular size of the enzyme both in the native membrane (submitochondrial vesicles) and in the reconstituted enzyme inserted into phospholipid vesicles containing lecithin. For both forms of the enzyme, we find the same molecular size, approximately 110,00 daltons. This size is consistent with a tetramer. Radiation results in fragmentation of the polypeptide and the destruction of the polypeptide correlates with loss of enzymic function. A similar size is obtained when purified D-beta-hydroxybutyrate dehydrogenase is inserted into a nonactivating mixture of phospholipid (i.e. in the absence of lecithin). We conclude that: 1) the native enzyme in submitochondrial vesicles and the purified active enzyme in phospholipid vesicles are the same size, approximating a tetramer; 2) radiation of D-beta-hydroxybutyrate dehydrogenase results in loss of activity and fragmentation of the polypeptide; and 3) the role of lecithin in activation of D-beta-hydroxybutyrate dehydrogenase is unrelated to determining oligomeric size of the enzymes since both active and nonactive forms exhibit the same structural size.

Activation of D-beta-hydroxybutyrate apodehydrogenase using molecular species of mixed fatty acyl phospholipids

D-beta-Hydroxybutyrate apodehydrogenase is a lipid-requiring enzyme with a specific requirement of lecithin for enzymatic function. The purified enzyme which is devoid of lipid can be reactivated with lecithin or mixtures of natural phospholipid-containing lecithin. However, it is mitochondrial phospholipid which activates the enzyme optimally and with kinetic parameters similar to that of the native membrane-bound enzyme. Mitochondrial phospholipid consists of three classes of phospholipid (lecithin:phosphatidylethanolamine:diphosphatidylglycerol in a ratio of approximately 2:2:1 by phosphorus); each class consists of a multiplicity of different molecular species due to diversity in the fatty acyl substituents. In this study, we have synthesized defined molecular species of mixed fatty acyl phospholipids to evaluate whether multiplicity of phospholipid molecular species are essential for optimal reactivation. We find that: 1) ternary mixtures of single molecular species of phosphatidylcholine, phosphatidylethanolamine, and phosphatidylpropan-1,3-diol in the liquid crystalline state mimic the optimal reactivation of the enzyme obtained with mitochondrial phospholipids; 2) although some negatively charged phospholipid appears necessary for optimizing the efficiency of activation, diphosphatidylglycerol can be replaced by phosphatidylpropan-1,3-diol, another negatively charged phospholipid; and 3) biphasic Arrhenius plots can be correlated with the liquid crystalline and gel states of the phospholipid.

Reactivation of D-beta-hydroxybutyrate dehydrogenase with short-chain lecithins: stoichiometry and kinetic mechanism

D-beta-Hydroxybutyrate dehydrogenase (BDH), purified as soluble, lipid-free apoenzyme (inactive) from either beef heart or rat liver mitochondria, can be reactivated by short-chain lecithins in the monomeric state. The enzyme was reactivated with dihexanoyl- [PC(6:0)], diheptanoyl- [PC(7:0)], and dioctanoyllecithins [PC(8:0)]. The titration curves of enzyme activity as a function of the phospholipid concentration are consistent with a model in which the enzyme contains two identical, noninteracting lecithin binding sites. The simultaneous occupation of these sites (via an equilibrium random mechanism) is required to activate the apoenzyme. Similar results were obtained with both rat liver and beef heart apoenzymes. The maximal velocities obtained with the different lecithins were similar [110-140 mumol of NAD+ reduced min-1 (mg of protein)-1]. The KL values (the apparent dissociation constants of the lecithin-site complexes) were 1.2 X 10(-4) M [PC(8:0)], 1.5 X 10(-3) M [PC(7:0)], and 4.5 X 10(-3) M [PC(6:0)] at 37 degrees C. This was confirmed by using phospholipase A2 to compete with the dehydrogenase for the lecithin monomers. Comparison of the delta G degrees values for complex formation with the different lecithins shows an average contribution of approximately 2.4 kJ/mol (0.9RT) per CH2 group. The interaction of the apolar moiety of lecithin with the protein seems to be essential for effective binding of phosphatidylcholine to apoBDH. The delta G degrees values, when combined with the estimated delta H degrees values, suggest that the binding of lecithin to the apoenzyme is approximately 60% enthalpy and approximately 40% entropy driven.

Renal vascular and tubular effects of vanadate in the anesthetized rat

The purpose of these experiments was to establish the renal vascular and tubular effects of vanadate. Three groups of adult rats were anesthetized with Na pentobarbital and given an i.v. infusion of a physiological saline solution at 0.055 ml/min. After a 60-min equilibration period, mean arterial blood pressure was measured, as were clearances of para-amino-hippuric acid (CPAH) and inulin (Cin), urine flow (V) and osmolality (Uosm) and the excretion rates of Na (UNaV), of K (UKV) and of Ca (UCaV). After the initial measurements, the i.v. infusion of physiological saline was continued in group 1 (controls), while vanadate was added to the saline and infused at 0.07 and 0.14 microM/min in groups 2 and 3. Then, all measurements were repeated. Compared with the control group, the following dose-dependent changes were observed in the vanadate-infused rats: increased mean arterial blood pressure, decreased CPAH (effective renal plasma flow), decreased Cin (glomerular filtration rate), increased V, UNaV and UCaV and decreased Uosm and UKV. Both the renal vascular and renal tubular effects of vanadate are similar to the renal effects of ouabain, previously reported by others. These effects can be explained by inhibitory effects of vanadate on Na,K-adenosine triphosphatase (ATPase) and/or Ca/ATPase activities of renal vascular and tubular cells.

Sodium-chloride-induced protection in nephrotoxic acute renal failure: independence from renin

It has been shown that the severity of experimentally induced acute renal failure (ARF) is inversely related to dietary sodium chloride intake, and the effects have been attributed to the concurrent changes in renal renin. In the current study, renal renin of rats was increased by chronic sodium deprivation and decreased by chronic sodium loading and DOCA administration. In two nephrotoxic models (mercuric chloride, uranyl nitrate), giving previously sodium-deprived rats 1% sodium chloride to drink for 48 hours prior to ARF induction greatly attenuated the severity without any reduction in their high renal renin. Conversely, giving previously sodium-loaded rats tap water to drink for 4 to 5 days prior to AFR induction greatly enhanced the severity without any increase in their subnormal renal renin. Therefore, the changes in severity of ARF resulting from changes in dietary sodium are not mediated by changes in renal renin. Significant inverse correlations were found between mean peak BUN values during the follow-up period (5 to 7 days) and the 24-hour urinary sodium excretions prior to ARF induction in both models, suggesting that sodium intake and/or excretion at the time of induction is a good predictor of the severity. The effects of sodium chloride in both models were predominantly expressed during the maintenance phase, and consisted of attenuation of the severity (both models) and hastening of the recovery (mercuric chloride model). Possible mechanisms by which dietary sodium produced its effects, independently of its effects on the renin-angiotensin system, are discussed.

Natriuresis-induced protection in acute myohemoglobinuric renal failure without renal cortical renin content depletion in the rat

The interrelationships of renal cortical renin content RCRC, sodium chloride excreting and the severity of renal failure were studied in the glycerol-induced acute myohemoglobinuric renal failure model in the rat. Protocols were designed to increase sodium chloride excretion without necessarily resulting in RCRC depletion. Our data fail to demonstrate a relationship between RCRC and severity of renal failure, but they demonstrate an excellent inverse correlation between the sodium chloride excretion of the animals in the 24 h prior to glycerol administration and the severity of resulitng renal failure. The protection of long-term saline-drinking animals should properly be ascribed to the associated natriuresis which develops much before RCRC depletion during the time course of saline drinking. The exact mechanism by which natriuresis exerts its protective effect needs further elucidation, but our data argue against a major role for RCRC in the pathogenesis of acute experimental renal failure.

Glycerol-induced acute renal failure in the two kidney Goldblatt rat

One to four weeks after the left renal artery was clipped and the contralateral kidney was left untouched in Sprague-Dawley rats (two-kidney Goldblatt preparation), the clips were removed under ether anesthesia and 10 ml/kg body wt of either 150 mM NaCl (control) or 50% glycerol in water (experimental) were injected intramuscularly. The next day the rats were anesthetized (sodium pentobarbital) and the renal function of both kidneys was measured, after which the renal cortical renin content was measured by incubation of tissue homogenate with angiotensinase-free rat renin substrate. Radioimmunoassay was used to determine the rate of angiotensin I production. Compared with controls, both kidneys of glycerol-injected rats had reduced GFR (left 28, right 18% of controls), increased percentage of fractional water excretion (left 5, right 6 times controls), and increased percentage of fractional Na excretion (left 3, right 4 times controls). Despite large differences in renal renin (left 28, 676, right 1,329 ng angiotensin I/h per mg protein), the extent of renal failure produced by glycerol was equal in the left and right kidneys. These results are inconsistent with the hypothesis that renal renin content is directly related to the severity of glycerol-induced renal failure in rats.