Effect of local heating of the rat testis on the levels in interstitial fluid of a putative paracrine regulator of the Leydig cells and its relationship to changes in Sertoli cell secretory function

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Abstract
Summary. Rat testes were exposed to heat (43°C) for 15 or 30 min to induce moderate or severe disruption of spermatogenesis, respectively. Over 3–42 days after treatment, testicular morphology and weight, the serum concentrations of FSH and the concentrations in interstitial fluid of testosterone, androgen-binding protein (ABP) and a factor(s) capable of stimulating Leydig cell testosterone secretion were monitored. Moderate seminiferous tubule damage induced by 15 min heat exposure caused a small decrease (20%) in testicular weight, but did not affect the other measures, other than transiently. In contrast, after exposure of testes to heat for 30 min there was a major and progressive decline in testicular weight throughout the experimental period, reaching 39% of control values by 42 days. In these animals, the serum concentrations of FSH were significantly increased (P < 0·01) throughout the period of study as also where the serum and interstitial fluid concentrations ABP (P < 0·05–0·01) and levels of interstitial fluid factor (P < 0·01). It is concluded that the activity of the interstitial fluid factor(s) can be increased by inducing severe but selective disruption of spermatogenesis, whereas moderate disruption has no effect. Moreover, as ABP secretion into interstitial fluid was increased after severe but not moderate disruption, this suggests that in such animals proportionately more ABP may be secreted via the base of the Sertoli cell. The parallel changes in activity of the interstitial fluid factor(s) and concentrations of ABP in interstitial fluid also provides further circumstantial evidence that these products may have a common (Sertoli cell) origin.