Endocrine research communications最新文献

The anterior pituitary gland can be involved in an inflammatory reaction mediated by lymphocytes that leads to various degrees of dysfunction. In seven rabbits immunized with homologous pituitary tissue in complete Freund's adjuvant, a focal lymphocytic infiltrate, and increased fibrosis was observed in five. These changes were patchy in distribution and limited to the anterior pituitary. No inflammation was observed in five control animals. When incubated with pituitary extract, partially purified lymphocytes from four of the five animals with altered pituitary histology demonstrated a significant (p less than 0.05) stimulation of 3H-thymidine incorporation. Measures of antipituitary antibodies using indirect immunofluorescence were negative in experimental as well as control animals. The present studies characterize the histologic changes and suggest that cellular immunity plays a role in the pathogenesis of experimentally induced autoimmune pituitary disease.

Enzymes of fatty acid activation and transport were studied in luteinized rat ovaries. Luteal mitochondria were found to contain high levels of palmitoyl-CoA synthetase and carnitine palmitoyl-transferase activities. In addition, studies on the effect of palmitate concentration on palmitoyl-CoA synthetase activity revealed the possible existence of two forms of the enzyme: Km values of 0.34 mM and 21.33 mM, with Vmax of 3.64 and 66.67 nmoles/min/mg mitochondrial protein respectively, were obtained for the two activities. Similar kinetic data for carnitine palmitoyl-transferase activity in intact mitochondria are a Km of 21 microM and a Vmax of 18.2 nmoles/min/mg mitochondrial protein. Only one activity of this enzyme could be detected in luteal mitochondria. It appears that the activities of both enzymes were not affected by prior administration of LH in vivo. The possibility that this negative finding was due to the experimental procedures employed, rather than a reflection of the situation in vivo, could not be discounted, although its more likely that these two enzymes are probably not locus of LH stimulation. The results indicate that fatty acid oxidation is an important metabolic capability of luteal mitochondria, and support the view regarding the lipid nature of the respiratory fuel of ovarian tissue.

By utilizing purified cytochrome P-450scc from bovine adrenocortical mitochondria and cholesterol-containing dioleoylglycerophosphocholine liposomes, we have demonstrated a dramatic stimulation (2-3 fold) of cholesterol binding to the steroid-free cytochrome by Ca++. We theorize that ACTH modulates the increase of intracellular Ca++ concentration resulting in the increase of the cholesterol availability to the mitochondrial cytochrome.

The Dunning R3327 rat prostatic adenocarcinoma contains specific binding sites for iodo-oPRL (ovine prolactin) in the membrane fraction (100,000 X g pellet). These are normally present at a low level, but immunization with oPRL produces a dramatic increase in tumor binding in either sex (females bear an implant of testosterone propionate pellet). Under these experimental conditions, the ventral prostate of rats bearing the tumors have no detectable PRL receptors. 5 alpha-Reductase activity, on the other hand, is lower in the tumors than in the normal prostates. Immunization also decreased somewhat the rate of growth of the tumors.

In vitro studies indicate that acute increases in intracellular phosphate concentration decrease red blood cell 2,3-diphosphoglycerate levels (G. Momsen, B. Vestergaard-Bogind, Arch Biochem Biophys 190:67, 1978). We have examined the relationship in vivo of serum phosphate concentration, red cell phosphate, 2,3-DPG and blood P50 in hyperglycemic dogs infused alternately with phosphate or chloride (control) solutions. During the 8-hr insulin infusion, serum phosphate (Pi) fell 40% in the chloride-treated animals and rose 71% in the phosphate-treated dogs (P less than 0.001, phosphate vs. control). RBC Pi concentration declined in the controls and rose significantly in the phosphate-infused dogs (P less than 0.02). Serum Pi and RBC Pi were correlated in the phosphate-managed animals (r = 0.76, P less than 0.02), but not in the controls. RBC 2,3-DPG failed to rise in either group during insulin infusion and regression analysis showed a negative correlation between serum Pi and 2,3-DPG (r = -0.90, P less than 0.005) and between RBC Pi concentration and 2,3-DPG (r = -0.84, P less than 0.02). P50 failed to change in either group during insulin treatment and for up to 24 hr after initiation of the 8-hr infusion of insulin.

It has been suggested that the oxygen bridge linking the two iodophenyl rings of the thyroid hormones at an angle of 120 degrees promotes electron transfer between the rings or establishes the proper stereochemical relationship between the rings. To determine the effects of oxygen bridge substitution on conformation, an analysis of the X-ray crystal structures of a number of oxygen bridge analogues (NH, CO, CHOH, S) was undertaken and the results compared with the thyroid hormone structures. The 3,5-iodine substituents cause the two phenyl rings to adopt a skewed or twist-skewed conformation. The phenyl rings of all bridge substituted analogues can adopt these hormone conformations. There is a correlation between the bridging bond length and the bridging angle that tends to keep the overall diphenyl ring conformation constant. The results of sulfur bridge substitution have further structural implications with regard to the design of novel hormone analogues.

We compared the disappearance rate of hGH and hGH20K injected into groups of mice. Radioactivity measurements and RIA were used to determine the amount of hormone in blood collected at various times after injection. The results indicate that the T1/2 value for hGH and hGH20K are equal. We conclude that there is no apparent relationship between the equal rates of disappearance, the dissimilar binding characteristics that have been shown for the hormones and their equipotent growth promoting activities.

RBC insulin binding was examined in Reye's survivors and families of affected patients to determine whether their previously reported hyperinsulinemic responses to oral glucose are accompanied by alterations in insulin binding and could contribute to the hypercatabolism seen in this disorder. The mean (125I)-insulin binding to 3 X 10(9) RBC's was 5.7 +/- SEM 0.4 percent in survivors compared to 6.6 +/- 0.3 in siblings (p less than .05) and 6.6 +/- 0.4 in control children (p = .05). Sex and maturity differences were found with higher binding values in men than women as well as higher values in men than boys. Receptor numbers in survivors were comparable to control values. Average affinities varied widely. Plasma insulin levels were low in the fathers (9 +/- SEM 1.4 uU/ml compared to 18.3 +/- 1.8 for control men and 20 +/- 4.5 for mothers of affected patients). The acute syndrome is accompanied by hypercatabolism in the presence of increased plasma insulin levels and familial clustering of cases and recurrences are known to occur. Reduction in insulin binding may play a role in the acute disease if such is shared by more traditionally hormone-responsive cells.

The renal phosphate transport response of thyroparathyroidectomized, vitamin D-deficient rats to the infusion of 1,25-dihydroxy vitamin D3 (1,25 D3) was studied with and without the simultaneous administration of a small (or "permissive") non-phosphaturic amount of bovine parathyroid hormone (bPTH). Although phosphate excretion (UPV) was unaltered by the infusion of either 0.1 U (= .0025 microgram or 6 pmoles) of 1,25 D3 or 0.2 U bPTH per hour for 6 hours, their combined administration reduced UPV from 14.8 +/- 1.6 to 10.3 +/- 1.2 microgram/min. (P less than .05). There were no alterations in inulin excretion. These data verify that: 1) 1,25 D3 is antiphosphaturic in this experimental setting in a very low dose which may represent a "physiological" amount of the metabolite; and 2) to enhance phosphate transport, the 1,25 D3 requires the presence of a small ("permissive") amount of PTH.

A study was made of the responses of the renin-angiotensin-aldosterone system (RAAS) produced in hyper- and hypothyroid rats maintained in a state of sodium depletion, as part of a wider study to effect a comparison with results previously obtained for the same parameters in rats maintained on a normal sodium diet and during experimental alterations of thyroid function. In hyperthyroid rats maintained on sodium deficient and normal sodium diet, and in euthyroid animals on a sodium deficient regimen, elevations of both plasma renin concentration (PRC) and serum aldosterone concentration (AC) were observed, while the plasma renin substrate (PRS) was decreased. In hypothyroid rats with normal sodium intake, PRC and AC were observed to be decreased relative to similar sodium-deficient animals. Relationships were observed between PRC and AC, and between AC and urinary sodium excretion. These results suggest that: i) Sodium depletion is a more effective stimulus than the thyroid hormones on the RAAS. ii) Aldosterone changes in sodium depletion are mediated by the RAS. iii) Sodium depletion appeared to induce a decrease in the hepatic synthesis of angiotensinogen.