Stimulation and suppression of the mineralocorticoid hormones in normal subjects and adrenocortical disorders

In summary, maneuvers that affect the RAS stimulate or suppress solely aldosterone and 18-OHB and have little, if any, effect on DOC, 18-OHDOC, B, or cortisol. The magnitude of aldosterone response seems to be of equal magnitude for all stimulatory or suppressive maneuvers as used in the present protocols. Although primarily originating in the ZG, some secretion of 18-OHB from the ZF is evident by its disproportionate responses (in relation to aldosterone) to maneuvers challenging ACTH. The prompt and marked increases the 18-OHDOC and B after ACTH make them the most sensitive "markers" of the ZF steroid activity. The application of those maneuvers and MCH measurements to adrenal disorders should help to further characterize their pathophysiology.

Use of OKT3 monoclonal antibody in the treatment of acute cardiac allograft rejection

OKT3 is a murine monoclonal antibody that recognizes the T3 surface antigen present on mature T cells, and it has been used to successfully treat renal allograft rejection. We report our experience with OKT3 in the treatment of cardiac allograft rejection. Eight patients with endomyocardial biopsy evidence of moderate or severe rejection were given fourteen daily intravenous treatments of OKT3. Six of the eight patients had complete recovery following OKT3 therapy; one required additional steroid therapy for recurrence and one patient failed to respond. Five of the six patients with a complete response have experienced no further rejection (mean follow-up 437 days). Adverse reactions to OKT3 were common early in the treatment course, but were well tolerated. We concluded that OKT3 is a safe and effective treatment of cardiac allograft rejection and that a majority of patients experience long-term rejection-free periods.

Calcium-sensitive uptake of amino acids by human placental slices

The placenta supplies many nutrients to the fetus, including amino acids by active transport. Although the exact regulatory mechanism is unknown, a few studies have suggested a role for calcium in amino acid transport. Therefore, we examined the relationship between calcium and amino acid uptake by term human placental slices. Calcium depletion of slices significantly reduced uptake of alpha-aminoisobutyric (AIB), which is actively transported primarily by a sodium-dependent, carrier-mediated mechanism. Impairment of AIB uptake induced by calcium depletion was reversed by repletion with calcium but not with other divalent cations. In contrast, uptake of phenylalanine, which is transported primarily by a sodium-independent mechanism, was not affected by calcium depletion. Uptake of leucine and valine, which accumulate by both sodium-dependent and independent mechanisms, was partially affected by calcium depletion. Verapamil (10 microM), an inhibitor of transmembrane calcium flux, significantly reduced AIB uptake. Trifluoperazine, a calmodulin antagonist, also inhibited AIB uptake. Analysis of AIB uptake kinetic constants for control and calcium-depleted slices showed no change in the diffusion constant, a 37% reduction in Vmax, and a 2-fold increase in Km. The results indicate that calcium may be an important factor in the cellular regulation of active transport of amino acids.

Effect of delta-9-tetrahydrocannabinol on the in vitro uptake of alpha-amino isobutyric acid by term human placental slices

Tetrahydrocannabinol (THC), the active component in marijuana smoke, crosses the placenta and is a potential fetotoxic agent. In both human and animal studies, the most consistent fetal effect of THC is intrauterine growth retardation. Since fetal somatic growth is dependent on placental transfer of nutrients, including essential amino acids, we studied the effect of THC upon the in vitro uptake of amino acid by term human placental slices. Uptake of alpha-amino isobutyric acid was inhibited in a dose-dependent fashion, correlating with the log of the dose (1-100 microM THC; r = 0.945; p less than 0.01). Compared to control tissue, significant impairment of alpha-amino isobutyric acid uptake began at 20 microM THC. Similar results were found for valine. The time course (30-120 min) for alpha-amino isobutyric acid uptake showed linearity for both control and THC-(50 microM) treated tissue, but there was a marked reduction in the THC slope. Uptake of alpha-amino isobutyric acid was significantly reduced at all times. The sustained effect of THC was slightly, but significantly, reversed by removal of THC from the medium after 90 min of 50 microM THC exposure. Only partial reversal may have been due to the 15- to 20-fold accumulation of THC in the placental tissue. Uptake kinetics showed noncompetitive inhibition with decreased Vmax: control Vmax = 51.66 +/- 6.26 versus 50 microM THC = 26.96 +/- 6.22 (mmol/liter intracellular water per h) (p less than 0.01); and no change in diffusion constant (Km): control Km = 0.78 +/- 0.08 versus 50 microM THC = 0.80 +/- 0.09 (mM).(ABSTRACT TRUNCATED AT 250 WORDS)

Tumor uptake of 5-fluorouracil, methotrexate, and adriamycin vs gallium

Since the imaging pattern of 67Ga-citrate is well known, it can be the benchmark for evaluation of potential tumor imaging agents. Tritium labeled 5-fluorouracil, Adriamycin, (doxorubicin/Adria) and Methotrexate/Lederle were compared at 2 h to 67Ga-citrate at 2 and 48 h by percent uptake per gram of various tissues and tumor in rats implanted with Walker 256 carcinosarcoma. 67Ga at 48 h showed approximately three times more uptake in the tumor than 5 fluorouracil and eight times more than the others. 5 Fluorouracil showed approximately three times greater uptake than Methotrexate or doxorubicin and 1.4 times the 2 h uptake of 67Ga. 5 Fluorouracil shows potential as an imaging agent especially where the waiting time between injection and imaging must be short.

Inhibition of Escherichia coli heat-stable enterotoxin effects on intestinal guanylate cyclase and fluid secretion by quinacrine

Enterotoxigenic Escherichia coli may produce a heat-stable enterotoxin (ST) that causes diarrheal disease in humans and in animals ST activates particulate guanylate cyclase in intestinal mucosal cells and causes intestinal fluid secretion. In this study, we examined the effects of quinacrine on ST activation of guanylate cyclase and ST-mediated intestinal fluid secretion. Quinacrine significantly reduced ST activation of particulate guanylate cyclase in rat intestinal tissue. Additionally, quinacrine reduced ST-mediated fluid secretion in a rat intestinal loop assay (P less than 0.05). In the suckling mouse model, subcutaneous quinacrine (0.1 mumole/mouse) reduced ST-induced fluid secretion at a submaximally effective dose of the toxin, but it did not reduce ST-mediated fluid secretion at a near maximally effective dose. Quinacrine (0.1 mumole/mouse) did not significantly reduce intestinal fluid secretion induced by the analog of cyclic GMP, 8-bromo cyclic GMP. However, at a higher concentration of quinacrine (1 mumole/mouse), significant inhibition of 8-bromo cyclic GMP-induced secretion was observed. Inhibition by the antimalarial agent quinacrine of ST-induced fluid secretion, by a block prior to guanylate cyclase activation, suggests a possible role for a phospholipase early in the sequence of events of ST activation of guanylate cyclase. The results suggest that ST may activate membrane phospholipases prior to ST activation of guanylate cyclase.

The mineralocorticoid hormone pathways in hypertension with hyperaldosteronism

Simultaneous measurement of the 0800-hr plasma concentrations of deoxycorticosterone (DOC), corticosterone (B), 18-hydroxycorticosterone (18-OHB), aldosterone, 18-hydroxydeoxycorticosterone (18-OHDOC) and cortisol (F) in four types of primary aldosteronism provides evidence for primary adrenal disease. Elevated DOC with normal F concentrations in the presence of elevated 18-OHB and aldosterone, and suppressed renin concentration suggests a primary adrenal abnormality of the zona glomerulosa (ZG). Steroid production by the zona fasciculata (ZF), F, 18-OHDOC, and most often B, is normal. These patterns exist only for primary adrenal hyperplasia, aldosterone-producing adenoma (APA), and aldosterone-producing adrenocortical carcinoma (AP-Ca). Elevated DOC levels are rarely found in patients with idiopathic hyperaldosteronism (IHA or adrenal hyperplasia) and suggest that IHA is not a primary adrenal disorder and should be excluded from the syndrome of primary aldosteronism as they have been heretofore.

Regulation of the mineralocorticoid hormones in adrenocortical disorders with adrenocorticotropin excess

Chronic stimulation by adrenocorticotropin (ACTH) of the adrenal cortex produces different plasma mineralocorticoid hormone (MCH) patterns, depending on the amount of glucocorticoid hormones (cortisol) concurrently generated and the degree of activation of the renin angiotensin system (RAS). Patients with Cushing's disease or the ectopic ACTH-excess syndrome have normal or low production of the MCHs, aldosterone and 18-hydroxycorticosterone (18-OHB), by the zona glomerulosa (ZG), elevated cortisol and deoxycorticosterone (DOC) levels, and high-normal to elevated production of the MCHs corticosterone (B) and 18-hydroxydeoxycorticosterone (18-OHDOC) by the zona fasciculata (ZF). Prolonged administration of superphysiologic doses of ACTH to normal subjects yields similar patterns. Patients with simple virilizing 21-hydroxylase deficiency (21-OHD) have impaired ZF production of B and 18-OHDOC and elevated DOC, 18-OHB, and aldosterone secretion secondary to the superimposed RAS stimulation of the ZG. Patients with 17 alpha-hydroxylase deficiency (17 alpha-OHD) have elevated levels of the ZF MCHs DOC, B, 18-OHDOC, and 18-OHB and a functionally suppressed ZG. Patients with 11 beta-hydroxylase deficiency (11 beta-OHD) have only elevated production of DOC by the ZF and suppressed RAS and aldosterone. A significant negative correlation between cortisol and aldosterone concentrations suggests that cortisol is involved in the ACTH-mediated inhibition of aldosterone formation.

Radiation therapy before cystectomy in the management of patients with bladder cancer

During the preceding two decades, 309 patients with bladder cancer were treated by irradiation before cystectomy at the Memorial Sloan-Kettering Cancer Center. A radical tumour dose averaging 6000 cGy (rad) in six weeks was given to 104 patients who underwent radical cystectomy +/- one year later for persistent or recurrent cancer. Pre-operative pelvic irradiation was planned in 205 patients who received either 4000 cGy in four weeks (119) or 2000 cGy in one week (86) and underwent radical cystectomy after +/- six weeks and two days, respectively. The determinate five-year survival rates (41-43%) were similar with the three irradiation regimes; mortality under five years was mainly due to cancer recurrence locally and/or distally. Incidence of recurrence with radiation-induced stage reduction (21%) was lower, especially within the pelvis, than with no stage reduction (51%). Treatment results with planned pre-operative irradiation, especially in high stage tumours, were more favourable with the shorter 2000 cGy regimen of high fractional doses than with the conventionally fractionated 4000 cGy regimen.

Inhibition of Escherichia coli heat-stable enterotoxin by indomethacin and chlorpromazine

Purified heat-stable enterotoxin (ST) from a procine strain of enterotoxigenic Escherichia coli activates quanylate cyclase in particulate fractions of rat intestinal tissue and induces fluid accumulation in suckling mice. These effects of ST were examined in the presence of either indomethacin or chlorpromazine. We also examined the effects of these two drugs on fluid accumulation in suckling mice induced by the 8-bromo analog of cyclic guanosine monophosphate. Either indomethacin or chlorpromazine reduced ST activation of guanylate cyclase. Both drugs also reduced intestinal fluid accumulation in suckling mice that resulted from submaximal doses of ST (both P < 0.001). However, there was no reduction in fluid secretion by either drug when a maximally effective dose of ST was used, suggesting that inhibition of fluid secretion by both drugs can be overcome by increasing the ST dose and that a threshold level of guanylate cyclase activity results in maximal secretory response. Both drugs also reduced basal guanylate cylase activity in rat intestinal tissue and fluid secreton in suckling mice. Chlorpromazine also reduced intestinal secretion mediated by 8-bromo cyclic guanosine monophosphate (P < 0.001). These findings indicate that chlorpromazine interferes with the effects of ST both before and after its activation of guanylate cyclase, whereas indomethacin interfers with ST only before its activation of guanylate cyclase.

Activation of intestinal guanylate cyclase by heat-stable enterotoxin of Escherichia coli: studies of tissue specificity, potential receptors, and intermediates

Heat-stable enterotoxin (ST) of Escherichia coli increased guanylate cyclase activity in homogenates of rat and rabbit intestinal mucosa and stimulated intestinal fluid secretion in suckling mice. The ST effect on guanylate cyclase was dose-dependent, occurred without a time lag, and was confined to the particulate fraction. ST activation of guanylate cyclase was tissue-specific; ST did not alter activity of soluble or particulate rat liver, lung, heart, kidney, or cerebral cortex enzyme. The ST activity on guanylate cyclase and secretion was methanol-soluble and alkali-labile, and its effects were not altered by phentolamine, propranolol, or atropine. Monosialoganglioside did not reduce ST-induced secretion. However, indomethacin and butylated hydroxyanisole decreased the ST effect on both guanylate cyclase and secretion. Fluid secretion with ST sppears to result from specific activation of particulate intestinal guanylate cyclase. While adrenergic and cholinergic events are probably not involved in this process, the effects of ST may be mediated through prostaglandin synthesis or oxidative mechnanisms.

Adrenocorticotropin inhibition of mineralocorticoid hormone production

1. Adrenocorticotropin (ACTH)-induced steroidogenesis, obtained by continuous administration of ACTH for 3 days, produces in man (a) sustained elevations of plasma deoxycorticosterone and cortisol concentrations, (b) transient elevations of plasma aldosterone and 18-hydroxycorticosterone concentrations that return to near-control values, and (c) brisk initial increases in plasma 18-hydroxydeoxycorticosterone and corticosterone concentrations that fall to 20-68% of peak values 30 h thereafter. 2. Dexamethasone (8 mg/day, orally) treatment for 2 days in man permits a greater postural increase in plasma aldosterone and 18-hydroxycortisone concentrations. A dampening effect of ACTH is suggested. 3. An ACTH-initiated inhibition of 11 beta- and 18-hydroxylation is proposed to be operative in regulation of mineralocorticoid hormones.