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SUMMARY
The effects of NADPH, NADP+, succinate and cyclic AMP on progestational steroid synthesis have been investigated in subcellular fractions of rabbit interstitial tissue. Production of progesterone and 20α-hydroxy-4-pregnen-3-one increased during incubation of mitochondria with NADPH and NADP+ respectively, and an increase in 20α-hydroxy-4-pregnen-3-one was observed after incubation of microsomes with NADP+. No changes in progestational steroid production were observed in individual cell fractions after incubation with cyclic AMP or succinate. However, a small but significant increase in progesterone synthesis occurred in a combined fraction containing mitochondria, microsomes and cytosol when incubated with cyclic AMP.
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SUMMARY
Rabbit ovarian homogenates were incubated in Krebs—Ringer bicarbonate buffer with or without glucose in the presence of citric acid cycle intermediates, α-glycerophosphate and lactic acid. The effects of these compounds on steroid synthesis were then observed. The inclusion of glucose alone in the medium was sufficient to increase progesterone biosynthesis. Succinate stimulated total progestational steroid synthesis both in the presence and absence of glucose in the medium, while citrate had an inhibitory effect in both cases. Malate stimulated synthesis only in the absence of glucose, while oxaloacetate and α-glycerophosphate stimulated synthesis only when glucose was present in the medium. Lactic acid had no effect in the absence of glucose, but significantly inhibited synthesis when glucose was present in the medium.
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SUMMARY
Luteinizing hormone and cyclic AMP stimulate synthesis of progestational steroids in rabbit ovarian homogenates. Both progesterone and 20α-hydroxypregn-4-en-3-one are produced and, in contrast to ovarian slice preparations, progesterone is the predominant steroid formed.
Steroid synthesis in homogenates from interstitial tissue is stimulated to a greater extent than in homogenates of luteal tissue. Synthesis of these steroids by the homogenates can also be increased by addition of NADP+ and NADPH. The amount and nature of the steroid synthesized varies with the amount of cofactor added and with its form (oxidized or reduced). When both forms of cofactor were added to the system in vitro, the ratio of the oxidized to the reduced form appeared to be important in determining the form of the steroid produced.
