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SUMMARY
The effects of unilateral and bilateral cryptorchidism and castration on serum concentrations of testosterone, FSH and LH in adult male rats were examined. The results provide no evidence for compensatory growth or development of the remaining scrotal testes up to 32 days after unilateral castration, although the scrotal testis of unilaterally cryptorchid rats showed enlargement when compared with those of control rats (P < 0·05) at 32 days. Unilateral treatments had few significant effects on serum hormones, but testosterone was increased on day 4 (P < 0·05) in unilaterally cryptorchid rats and on day 32 (P < 0·05) in unilaterally castrated rats, compared with controls, and FSH levels were higher in unilaterally castrated rats on day 16 (P < 0·05). Bilateral cryptorchidism caused an increase in serum FSH within 4 days (P < 0·05) and in serum LH by 8 days (P < 0·05) after surgery, with both hormones reaching levels double those found in control rats (P < 0·01) by day 16, while testosterone levels were maintained at or above control values. Bilateral castration resulted in a marked decrease in testosterone levels (P < 0·01) and a sharp increase in serum gonadotrophins. FSH had nearly doubled (P < 0·01) and LH had increased fourfold (P < 0·01) 4 days after castration, their levels reaching 773% (LH) and 287% (FSH) of control values by 32 days (P < 0·01). The observations support the hypothesis of a separate, testosterone-independent feedback system of the testis on the hypophysis.
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Animal Reproduction Teaching and Research Center, The Ohio State University, Columbus, Ohio 43210, U.S.A.
(Received 26 September 1974)
While it is widely recognized that androgens appear to be essential for maintenance of the spermatogenic process in a variety of scrotal mammals (Steinberger, 1971) and that ambient temperatures exceeding the thermoregulatory capabilities of the scrotum and pampiniform plexus are detrimental to sperm production, surprisingly little information is available concerning the effects of heat on the enzymology of testicular steroidogenesis (VanDemark & Free, 1970). Hall (1965) has demonstrated that incorporation of [1-14C]acetate into [14C]test-osterone by rabbit testis slices in vitro is maximal at the scrotal temperature and depressed at the abdominal temperature. The data of Le Vier & Spaziani (1968), using non-replicate experiments, suggest that testicular conversion of [4-14C] cholesterol to [14C]pregnenolone (cholesterol side-chain cleavage enzyme, CSCCE) in the rat exhibits a positive in-vitro temperature coefficient over a range of 28–36 °C
