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J. S. H. ELKINGTON and A. W. BLACKSHAW

Summary.

A factorial experiment, using injections of oestradiol, testosterone and pregnant mare serum gonadotrophin (pmsg), has been used to show the main effects and the interactions of these hormones on the rat testis. Oestradiol caused a decrease in testis and seminal vesicle weight, seminiferous tubule diameter, lactate (LDH) and glucose-6-phosphate (G-6-PDH) dehydrogenase activity in the interstitial tissue, and cessation of spermatogenesis at the pachytene primary spermatocyte stage. Testosterone and pmsg antagonized most of these effects, but testosterone alone caused a decrease in activity of LDH and G-6-PDH in the interstitial tissue, and pmsg did not influence the effect of oestradiol on the seminal vesicle weight.

Oestradiol significantly decreased the activity of the unusual isoenzyme of LDH (LDH-X) in the rat testis, and it seems likely that the induction of LDH-X synthesis occurs during the pachytene primary spermatocyte stage of spermatogenesis. Testosterone and pmsg stimulated LDH-X synthesis when combined with oestradiol, while testosterone, but not pmsg, caused stimulation of LDH-X synthesis when injected alone.

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A. W. BLACKSHAW and J. S. H. ELKINGTON

Summary.

The body and testis weights increase linearly with time during growth of the immature rat. Between 20 and 30 days of age, there is an increase in lactate dehydrogenase (LDH) activity in the interstitial and tubular tissue of the testis and glucose-6-phosphate dehydrogenase (G-6-PDH) in the interstitial cells. LDH-X isoenzymes appear between 20 and 30 days of age and are associated with the seminiferous tubular epithelium. There is a linear increase in seminiferous tubule diameter with age until 60 days, after which time there is no further tubular growth.