The influence of sex differences, skin-shedding cycle and hibernation on the regulation of aspartate and alanine aminotransferase activities in the grass-snake, Natrix n. natrix (L.)

Abstract

1. 1. In the grass-snake, Natrix n. natrix (L.), sex difference are known to have a considerable effect on the regulation of the activities of ASAT, and especially of ALAT. 2. 2. During the inter-moult period the ALAT activities are found to be significantly higher in the liver and serum of the males, the serum activities being higher also during skin-shedding. 3. 3. The very high activity of the enzyme in the serum of the males probably depends on the regulatory effect of a specific protein—the “reptile protein binding testosterone” (RPBT) which binds this hormone on the competitive basis. 4. 4. The activity of ASAT is also relatively higher in the liver and serum of the males. In the course of the shedding cycle no changes in the regulation of the enzymic activities could be seen. 5. 5. The ratios of average hepatic amino transferase activities are clearly different in each sex. However, the ratios of average serum AT activities represent a different range of values. 6. 6. In males, they all confirm the predominance of ALAT activities in the enzymic regulation of the homeostasis of the liver, and of the serum in particular. 7. 7. During moult, the observable changes in the activities of ASAT and ALAT in the liver and serum do not indicate a lowered thyroxin level in the serum of the snakes under study, as postulated by the hormonal model of this process. 8. 8. During hibernation, changes in the regulation of the activities are related primarily to three processes. First, a lowered ASAT activity in the liver differs from that of ALAT. Second, the dispersion of the activities of both enzymes decreases considerably. Third, the numeric values of the ratios of average activities grow for the liver, but they decrease for the serum.