Adenosine deaminase attenuates canine coronary vasodilation during systemic hypoxia

The hypothesis that adenosine mediates the coronary vasodilatory response to hypoxia was tested by determining if intracoronary infusion of the adenosine degrading enzyme, adenosine deaminase (ADA), would attenuate this response. Efficacy of ADA was also evaluated by examining its effect on the coronary responses to exogenous adenosine and to 20-s myocardial ischemia. Experiments were conducted in 14 anesthetized, open-chest dogs ventilated 3-5 min with 3% O2-5% CO2-92% N2 to induce systemic hypoxia. Under control, pre-ADA conditions, hypoxia (arterial PO2 19 +/- 2 mmHg) caused left anterior descending (LAD) coronary blood flow to increase from 100 +/- 12 to 382 +/- 47 ml X min-1 X 100 g-1 (+282%). After infusion of ADA (5 U X kg-1 X min-1 for 8-10 min) into the LAD, equally severe hypoxia (arterial PO2 18 +/- 3 mmHg) caused a significantly smaller increase in LAD flow, 79 +/- 9 to 234 +/- 41 ml X min-1 X 100 g-1 (+195%). Oxygen consumption in the LAD perfusion field was unchanged by hypoxia before ADA but fell significantly during hypoxia after ADA. ADA also attenuated significantly the coronary vasodilatory response to exogenous adenosine and to 20-s ischemia. The results of this investigation demonstrate a significant role of adenosine in the coronary vasodilatory response to systemic hypoxia.

Cardiac and coronary effects of prazosin and phenoxybenzamine during coronary hypotension

Left coronary perfusion pressure was reduced to 50 mm Hg in alpha-chloralose-anesthetized open chest dogs, causing significant reductions in coronary blood flow and left ventricular oxygen consumption (P less than .05). Infusion of the specific alpha-1 adrenergic antagonist prazosin (0.1 mg/min i.c.) during coronary hypotension significantly increased coronary flow and oxygen consumption within 6 to 8 min. These effects of prazosin were not attenuated by beta adrenergic blockade with propranolol. In the absence of propranolol, infusion of the nonspecific alpha adrenergic antagonist phenoxybenzamine (0.37 mg/min i.c.) increased coronary flow and oxygen consumption within 10 to 15 min, and these increases were significantly greater than with prazosin. In the presence of propranolol, phenoxybenzamine caused increases in coronary flow and oxygen consumption that were not different from those caused by prazosin. The results indicate that 1) prazosin increases coronary flow and oxygen delivery by abolition of a coronary constrictor tone mediated by postsynaptic alpha adrenoceptors; 2) the increases in coronary flow and oxygen consumption caused by phenoxybenzamine in the absence of beta adrenergic blockade were due to antagonism of pre- and postsynaptic alpha adrenoceptors; and 3) the increases in coronary flow and oxygen consumption caused by phenoxybenzamine after beta adrenergic blockade were due entirely to antagonism of coronary postsynaptic alpha-1 adrenoceptors.

Alpha 1-adrenergic blockade increases coronary blood flow during coronary hypoperfusion

Coronary hypoperfusion was elicited in alpha-chloralose-anesthetized open-chest dogs by reducing left coronary perfusion pressure to 50 mmHg. Left coronary blood flow, as well as left ventricular oxygen extraction, oxygen consumption, and contractile force were measured. The reduction in perfusion pressure caused significant reductions in coronary flow, oxygen consumption, and peak reactive hyperemic flow. During hypoperfusion in 11 dogs, intracoronary infusion of the specific alpha 1-adrenergic antagonist prazosin (0.1 mg/min) increased coronary flow and oxygen consumption by 22 and 16%, respectively. Peak increases were observed after 6-8 min of prazosin infusion (0.6-0.8 mg prazosin), and both increases were statistically significant (P less than 0.05). In seven additional dogs, beta-adrenergic blockade with propranolol (1.0 mg ic) did not significantly affect the actions of prazosin. In five additional dogs, the specific alpha 2-adrenergic antagonist yohimbine (1.3 mg ic) in the presence of propranolol (1.0 mg ic) did not affect coronary flow or oxygen consumption during coronary hypoperfusion. Those results suggest that an alpha 1- but not an alpha 2-adrenergic constrictor tone was operative in the left coronary circulation under the conditions of these experiments.

Androgens in various fluid compartments of the rat testis and epididymis after hypophysectomy and gonadotropin supplementation

Hypophysectomized male rats were administered LH or LH + FSH for 14 days and subjected to in vivo micropuncture collection of reproductive tract fluids to determine if FSH alters the compartmentalization of testosterone in the rat testis or of 5 alpha-dihydrotestosterone (DHT) in the epididymis. Testosterone and DHT concentrations were determined in cardiac blood serum, testicular venous serum, testicular interstitial fluid, and seminiferous tubule fluid, and in intraluminal fluid and tissue extracts from the caput and cauda epididymidis. Testosterone is the predominant androgen in the testis, and compared with control values, concentrations in venous sera, interstitial fluid, and tubule fluid were returned to values indistinguishable from controls by supplementation with 24 micrograms LH/day. 24 micrograms LH + 24 micrograms FSH/day did not augment the intratubular partition of testosterone. Epididymal DHT values were returned to control levels by LH alone, but additional supplementation with FSH significantly increased DHT from the caput epididymidis even further. It is speculated that FSH does not alter the compartmentalization of androgens in the rat testis, but may play a role in retaining androgens in the epididymis.

Androgens in male rat reproductive tract fluids: hypophysectomy and steroid replacement

The control of androgen concentrations in the intraluminal fluids of the male reproductive tract is not well understood. The present experiments were performed to determine the effects of hypophysectomy, hypophysectomy plus testosterone (T), and hypophysectomy plus pregnenolone treatment on intraluminal androgen concentrations in the adult rat testis and epididymis. T and 5 alpha-dihydrotestosterone (DHT) concentrations were determined in the vascular, interstitial, and intraluminal compartments of the epididymis. Testicular and epididymal morphology also were examined under light microscopy. Hypophysectomy of at least 5 days duration significantly reduced T and DHT concentrations in serum, tissues, and intraluminal fluids of the reproductive tract. T replacement for 14 days, which produced peripheral T concentrations of 5 ng/ml, did not support intraluminal androgen concentrations in the seminiferous tubules equivalent to controls; rete testis androgen concentrations were similar to controls, however. Pregnenolone administration at 2 mg X rat-1 X day-1 for 14 days did not maintain spermatogenesis nor intraluminal T concentrations in the seminiferous tubules equivalent to controls; however, a low level of spermatogenesis continued when intraluminal and tissue androgen concentrations were maintained at 10-20% of controls by either the testosterone and pregnenolone treatments.

Local endogenous opiate activity in dog myocardium: receptor blockade with naloxone

The participation of endogenous opiates in myocardial performance and coronary blood flow was investigated. Heart rate, left ventricular contractile force (LVCF), left coronary blood flow (LCBF), and left ventricular oxygen extraction were monitored in anesthetized dogs before and after intracoronary opiate receptor blockade with naloxone. LVCF consistently increased in a dose-dependent fashion following intracoronary naloxone. The increasing LVCF was accompanied by significant increases in LCBF and myocardial oxygen consumption, without changes in heart rate. Rapid onset of responses suggested the presence of endogenous opiates operating locally within the myocardium. Similar effects did not follow right atrial injection of naloxone, ruling out a systemic mechanism. Furthermore, naloxone injected into the isolated left anterior descending artery selectively increased contractile force in that perfusion territory while the adjacent untreated circumflex territory showed no change. The administration of dynorphin into the coronaries produced a depression of LVCF qualitatively consistent with these effects. The effect of dynorphin was subsequently reversed with naloxone. These results support the concept that endogenous opiates participate in the regulation of myocardial function through local mechanisms at the myocardial level.

Role of the occupational health service in screening and increasing the uptake of rubella immunisation

An occupational health department in a district general hospital in Newcastle upon Tyne screened 487 women of childbearing age for rubella immunity who were prospective employees and whose immunity state was unknown. Ninety per cent of these women were immune. Of the 51 who were found to be susceptible, 29 accepted vaccination.

Adenosine antagonist aminophylline attenuates pacing-induced coronary functional hyperemia

The role of adenosine in pacing-induced hyperemia was examined in 10 dogs. Left coronary blood flow (LCBF), left ventricular O2 extraction [(a-v)O2], and myocardial O2 consumption (MVO2) were monitored. Heart rate (HR) was initially paced at 120 beats/min and then increased to 180 beats/min to elicit a hyperemic response (delta LCBF). During the hyperemia, the vasodilatory response to exogenous adenosine (FAd) was tested. HR was then returned to the initial level, and 20 min after injection of aminophylline (100 mg iv) HR was again increased to 180 beats/min. The response to adenosine was again tested. The pacing-induced increase in MVO2 (delta MVO2) was not affected by aminophylline (P greater than 0.05). However, after aminophylline, the flow response slope delta LCBF/delta MVO2 was decreased by about 20% (P less than 0.05), and the extraction-response slope delta (a-v)O2/delta MVO2 was increased by 100% (P less than 0.05). FAd was also decreased by aminophylline, and the magnitude of the reduction was correlated with the decrease in the flow-response slope (r = 0.82). These results suggest that endogenous adenosine may play an important role in coronary functional hyperemia induced by increases in heart rate.

On the androgen microenvironment of maturing spermatozoa

Adult anesthetized male rats were submitted to in vivo micropuncture of the seminiferous and epididymal tubules and reproductive tract vasculature to obtain fluids for analysis of testosterone, 5 alpha-dihydrotestosterone, and androgen-binding protein (ABP). Androgen and ABP concentrations were determined by RIA. The highest concentrations of testosterone (73.14 +/- 5.12 ng/ml) were in testicular interstitial fluid. A significant downhill concentration gradient exists between testosterone concentrations in testicular interstitial fluid and seminiferous tubule fluid (50.24 +/- 2.26 ng/ml); another significant decrease occurs between seminiferous tubule fluid and rete testis fluid (17.85 +/- 2.11 ng/ml). 5 alpha-Dihydrotestosterone concentrations were highest in intraluminal caput epididymidal fluids (58.73 +/- 6.48 ng/ml) as were ABP concentrations (33.30 +/- 2.40 mu leq/microliter). Intraluminal sperm concentrations were also determined, and from these data, fluid reabsorption by the efferent ducts and epididymal tubules were calculated. Eighty-nine percent of the fluid leaving the testis is reabsorbed between the rete testis and caput epididymidis, and 96% is reabsorbed between rete and cauda. It was calculated that large losses of androgen and ABP also occur from the lumen of the excurrent duct system. These losses may be due to metabolism, diffusion from the lumen, or uptake by cells.

Identification of the metabolites of erythro-9-(2-hydroxy-3-nonyl)hypoxanthine from laboratory animals

After administration of erythro-9-(2-hydroxy-3-nonyl)hypoxanthine, eight compounds were isolated from the urine of rats, dogs, and monkeys. All of the drug metabolites were modified on the nonyl side chain. The oxidatively degraded metabolites included an alcohol (9-(2,8-dihydroxy-3-nonyl)hypoxanthine), the corresponding ketone (erythro-9-(2-hydroxy-8-keto-3-nonyl)hypoxanthine), and three carboxylic acids [erythro-6-hydroxy-5-(9- hypoxanthyl ) hepanoic acid, erythro-7-hydroxy-6-(9- hypoxanthyl )octanoic acid, and erythro-8-hydroxy-7-(9- hypoxanthyl )nonanoic acid]. Glucuronide conjugates of the unchanged drug and the alcohol metabolite were also found. The alcohol, ketone, and nonanoic acid metabolites were produced by all three species. Only the rat produced the shorter chain acid derivatives and no glucuronides. The monkey excreted both glucuronides, while dogs formed one glucuronide conjugate, that of the parent drug.

Absence of generalized immunosuppression in C57BL/6J mice implanted with Lewis T241 fibrosarcoma or Lewis lung carcinoma

The immune status of C57BL/6J mice implanted with Lewis T241 fibrosarcoma or Lewis lung (LL) carcinoma was investigated on days 14 and 28 after implantation. Splenic lymphocyte responses were assessed in mitogen (Con A, LPS) mixed lymphocyte culture (MLC), natural killer (NK), graft-vs-host (GVH), and interleukin production assays. Except for NK-cell cytotoxicity, all other immunologic parameters were either comparable to those in medium-implanted controls or augmented. NK cytotoxicity was reduced in both tumor-bearing groups on day 28. The provision of NK potentiation therapy (beta-interferon, polyinosinic: polycytidylic acid) to T241 mice under various treatment conditions did not have any significant effect on lung metastasis or survival. The results of this study do not support the thesis that T241- or LL-bearing C57BL/6J mice are generally immunosuppressed. Indeed, when immune functions were assessed on the basis of total splenic activity, each of the measured immunologic parameters was substantially greater in animals with tumors than without. Further it seems improbable, considering the magnitude of the NK-cell defect in T241 mice on days 14 and 28 after implantation and the absence of a therapeutic response to NK-cell stimulants, that NK-cell cytotoxicity is intrinsically associated with resistance to tumor progression in this model.

Simple method for quantifying pulmonary metastases in a murine fibrosarcoma

A simple method is described for quantitating pulmonary metastases in C57BL/6J mice implanted with the Lewis T241 fibrosarcoma. Lungs were removed from tumor-bearing mice, homogenized, and diluted to 14 ml with supplemented Roswell Park Memorial Institute Tissue Culture Medium 1640 (+5% fetal calf serum). Twenty-five microliters of lung suspension from individual mice were added to a flat-bottomed microtiter plate containing 175 microliters of supplemented media, pulsed with [3H]thymidine, and incubated for 20 hr at 37 degrees. The cells were processed with a multiple automated sample harvester and counted in a liquid scintillator. Total lung burden was extrapolated from measured radioactivity (as cpm) through the use of a standard curve. This method is reasonably accurate and precise and provides more quantitative information on the pulmonary metastatic process than most conventional assays.

Radioimmunoassay for immunoglobulin G autoantibody on the surface of mouse erythrocytes

A radioimmunoassay (RIA) for the determination of autoantibody on the surface of erythrocytes from New Zealand Black (NZB) mice is described. This method was adapted to hemagglutination plates in order to facilitate the separation of bound and unbound 125I-labeled rabbit anti-mouse immunoglobulin G with an automated cell harvester. Intra- and interday precision, over the useful quantitative range of the standard curve, was 3.9 and 12.9%, respectively. The RIA was five to ten times more sensitive than the direct antiglobulin test which, unlike the RIA, provided little quantitative information on a group of 20 experimental NZB mice. This is publication number 562 from the Department of Basic and Clinical Immunology and Microbiology, Medical University of South Carolina.

Sensitive and selective assay for adenosine using high-pressure liquid chromatography with fluorometry

A new method for quantitation of adenosine was tested in canine myocardial extracts. The method involves incubation of the extract with chloroacetaldehyde to form the fluorescing adenosine derivative 1, N6-ethenoadenosine. The ethenoadenosine is separated by high-pressure liquid chromatography (HPLC) and quantitated by fluorometry. Experiments demonstrated that 1) the method is selective for adenosine, 2) fluorescence peak height is linearly related to the quantity of ethenoadenosine, and 3) adenosine in the extract is quantitatively converted to ethenoadenosine by the incubation procedure. Also, within the range of adenosine concentrations seen in five extracts, estimates of myocardial adenosine content with the fluorometric method were nearly identical to those using the more routine technique of HPLC with direct detection by ultraviolet (UV) absorption. A primary advantage of the fluorometric method is its greater sensitivity. As little as 0.50 pmol on the column could be quantitated by fluorescence, compared with approximately 20 pmol with UV absorption. Because of the greater sensitivity, the fluorometric method should be more easily applied to samples with smaller adenosine concentrations.

Radioimmunoassay of the immunomodulator erythro-9-(2-hydroxy-3-nonyl)-hypoxanthine in human serum and urine

A radioimmunoassay was developed for the measurement in human serum and urine of erythro-9-(2-hydroxy-3-nonyl)-hypoxanthine. Antisera were produced in rabbits by immunization with an erythro-9-(2-hydroxy-3-nonyl)-hypoxanthine hemisuccinate-bovine serum albumin conjugate. The competitive antigen was erythro-9-(2-hydroxy-3-nonyl)-hypoxanthine labeled with carbon-14 on the purine ring. Cross-reactivities were measured against three metabolites and the naturally occurring purine bases inosine and hypoxanthine. Sensitivity of the method was 1 ng/ml in serum and 10 ng/ml in urine. Precision at clinical levels was +/- 15% in serum at 2 ng/ml and +/- 3% in urine at 200 ng/ml.

Renal responses of the cardiac-denervated nonhuman primate to blood volume expansion

Experiments were performed to determine whether total, specific cardiac denervation affects the renal responses of the nonhuman primate to acute intravascular volume expansion. Adult male Macaca fascicularis monkeys underwent chronic intrapericardial cardiac denervation or sham surgery. After a 14- to 30-day recovery period, each animal was anesthetized with sodium pentobarbital and estimated blood volume was volume-expanded 20% with 6% dextran in isotonic saline. Control renal excretory function did not differ between the two groups, and both groups had similar increases in urine flow, sodium and potassium excretion, osmolar clearance, free water clearance, and renal plasma flow after volume expansion. The times to peak diuresis and natriuresis also were similar in both groups. These results demonstrate that the cardiac-denervated monkey shows unattenuated renal excretory responses to volume expansion. This could indicate that either cardiac receptors do not play a major role in eliciting these responses in the primate or that eliminating a role of cardiac afferents is compensated for by redundant afferents from arterial baroreceptors.

Reduced resistances of septal artery collateral channels after cardiac sympathectomy

We have shown that chronic cardiac sympathectomy reduces coronary collateral resistances. The present experiments in isolated dog hearts delineated the role of intramyocardial collateral channels from the septal (SEP) to the circumflex (CIRC), left anterior descending (LAD), and right (RT) coronary arteries in this phenomenon. In 11 controls and 8 2-wk sympathectomized hearts, a retrograde flow technique was used to determine collateral resistances between the epicardial arteries (CIRC, LAD, RT). Collateral resistances between the CIRC and LAD and between the LAD and RT were 42-68% less in sympathectomized hearts (P less than 0.05). Collateral resistances from the SEP to each epicardial artery were determined from retrograde flows simultaneously collected on each epicardial artery when the SEP was the only vessel perfused. Collateral resistances from the SEP to the CIRC and LAD were 51-59% less in the sympathectomized hearts (P less than 0.05). Thus, intramyocardial channels from the SEP to the left coronary arteries show reduced resistances after sympathectomy and can provide a substantial portion of the increased collateral flow to these vessels.

Alexandrite-laser performance at high temperature

The performance of a flash-pumped alexandrite laser operating in a long-pulse mode has been characterized at temperatures from 34 to 310 degrees C. Laser gain and efficiency increased monotonically up to 225 degrees C, with a peak pulse energy there more than four times the value at 34 degrees C. The output wavelength also increased monotonically from the 34 degrees C value of 752 nm to a maximum of 790 am at 310 degrees C.

Effect of aminophylline on coronary functional hyperemia and myocardial adenosine

The role of adenosine in coronary functional hyperemia was tested using the adenosine antagonist aminophylline. In 11 dogs left coronary blood flow (LCBF) and left ventricular oxygen extraction [(a-v)O2] were monitored. Myocardial oxygen consumption (MVO2) was calculated. Before aminophylline was administered, intracoronary infusion of 6.8 micrograms/min norepinephrine increased LCBF and MVO2 by 40-80%. Simultaneous infusion of adenosine further increased LCBF. Fifteen minutes after injection of 100 mg aminophylline, norepinephrine still increased LCBF, and the ratio delta LCBF/delta MVO2 was unchanged (P greater than 0.05). Although the functional hyperemia was not blunted, the response to infused adenosine was abolished by aminophylline. In 20 additional dogs myocardial adenosine was determined. Before norepinephrine infusion myocardial adenosine with and without aminophylline was 12.7 and 14.3 nmol/g dry wt, respectively (P greater than 0.05). During norepinephrine infusion an increase in adenosine correlated well with increases in MVO2 and LCBF, but the increase in adenosine was not greater after aminophylline. Thus the failure of aminophylline to blunt functional hyperemia was not due to a higher adenosine level after aminophylline. These results do not support a role for adenosine in functional hyperemia elicited by norepinephrine.