The corpus luteum periodicum in the bitch: histochemical and biochemical investigations during different phases of the cycle.

The corpus luteum periodicum (c.l.p.) of the bitch was studied using enzyme histochemistry, clinical and biochemical methods. Assessment of variations of the serum progesterone level during different stages of the ovarian cycle and the study of enzymatic activity of the luteal tissue furnished informations on vitality and biosynthetic capacity of luteinizing cells: The period of functional activity of the c.l.p. nearly ceased about day 60 of the cycle (proestrus included) in the animals examined. In the light microscope the neo-synthesis of progesterone in the c.l.-tissue can be made visible by histochemical demonstration of the activity of Delta(5)-3 beta-hydroxysteroiddehydrogenase (3 beta-HSD) only up to a progesterone level exceeding 6.7 ng/ml plasma. The data obtained contribute to our baseline knowledge of the mechanism involved in the etiology of pseudopregnancylike conditions in the bitch.