Basic Chromosomal Proteins in Evaluation of the Arrest and Restoration of Spermatogenesis1, 2

The amino acid incorporation and weight ratios of lysine rich histone fractions TH1-x, which is synthesized at primary spermatocyte stages and H1, which is synthesized at spermatogonial stages of seminiferous epithelial cells of rat testis, provide an index for the evaluation of the interruption and restoration of early stages of spermatogenesis. The basic chromosomal proteins of the testis can be used as marker proteins in an alternative method for the assay of the effects on spermatogenesis exerted by hormones and inhibitors. The method was tested here by application to two previously studied procedures for interruption of spermatogenesis, viz. hypophysectomy and elevated testicular temperature. After hypophysectomy, the ratios TH1-x/H1 by weight and by amino acid incorporation decreased progressively, but these ratios increased toward normal values during repeated administration of gonadotropic hormones (FSH + LH) or testosterone (T). The effectiveness of the hormones was in the order: T≥LH + FSH = LH>FSH. These observations support the previously held view that T is required in the conversion of spermatogonia to primary spermatocytes. The testis specific protein (TSP), which is synthesized in early spermatid stages, disappeared approximately 15 days after hypophysectomy and the TSP/H4 ratio of incorporation was markedly decreased by 5 days after hypophysectomy indicating that early to middle stage spermatids are particularly sensitive to deprivation of FSH and LH (or T). Elevation of testicular temperature to 40.5°C for 1–4 h followed immediately by in vitro incubation with [3H] amino acids resulted in a decrease in specific activity of histone fraction H1 to a significantly greater extent than that of TH1-x relative to unheated controls and consequently the TH1-x/H1 incorporation ratio increased. However, the TH1-x/H1 ratios of incorporation and weight decreased below normal 1–3 days after the heat treatment. At 13–29 days after the period of elevated temperature, the TH1-x/H1 ratio of amino acid incorporation had returned to normal, but the ratio by weight was still below control values. These data are interpreted to indicate that late stage spermatogonia are more sensitive to elevated temperature than primary spermatocytes or early stage spermatogonia. Early to middle stage spermatids are particularly temperature sensitive as shown by the fact that TSP/TH1-x, TSP/H1 and TSP/H4 incorporation ratios decreased sharply as a result of elevated testicular temperature in vivo or elevated temperature of incubation in vitro.