B. Cook

The duration and control of adrenal function in adenohypophysectomized cockerels

Abstract Corticosterone concentration in adrenal venous plasma of adenohypo-physectomized cockerels was about one-third of that found in intact birds. There was no change in the output of this steroid into the adrenal vein from 1.5 to 42 days after surgery. Corticosterone synthesis in vitro was not influenced by hypothalamic homogenate, suggesting that no corti-cotrophin was present in this tissue, although evidence supports the existence of an extrahypophyseal corticotrophin. ACTH was shown to act at step(s) in the metabolic pathway preceding progesterone. The significance of these results is discussed and it is concluded that adrenal regulation in cockerels cannot be explained by the traditional concepts associated with mammalian adrenal function.

The influence of some steroids, including estrogens, on progesterone synthesis in vitroby porcine corpora lutea

Abstract Porcine corpora lutea were incubated with several concentrations of progesterone, 5-pregnene-3 β -ol-20-one, 20 α - and 20 β -hydroxy-4-pregnene-3-one (0.001–0.064mM) and estrone, estradiol and estriol (0.000156-0.064mM). All the compounds, except estrone, inhibited acetate incorporation into progesterone though none of them influenced progesterone synthesis from endogenous tissue sources. Estrone, the only ineffective steroid, is the major excretory estrogen in pigs. Progesterone synthesis from endogenous tissue sources and acetate incorporation into progesterone showed totally different responses to increasing steroid concentrations, showing that these parameters relate to different biochemical processes. Even though the estrogens were tested through a wide range of concentrations, no steroidogenic effect of these compounds was detected in this in vitro system. When corpora lutea were incubated with slices of ovarian stromal and follicular tissue, progesterone synthesis was not affected. It is concluded that steroids play a minor role in the direct control of progesterone synthesis by porcine corpora lutea.

Comparative Studies on Progesterone Synthesis In Vitro—Thoughts on Corpus Luteum Formation

Duncan, Bowerman, Hearn and Melampy (1960) and Duncan, Bowerman, Anderson, Hearn and Melampy (1961) first showed that porcine corpora lutea when incubated in an in vitro system can be caused to synthesize progesterone. Since that time a considerable amount of work has been published dealing with the rate of progesterone synthesis by corpora lutea of rats, cows, and women. The significant difference between Duncan’s original work and that dealing with corpora lutea from non-porcine species lay in the fact that both the cow and human corpora lutea responded to the addition to the medium of LH-containing hormones by significant increases in progesterone synthesis while porcine corpora lutea were said to be unable to show such a response. These species differences and the possible causes underlying them were of interest to us.