EFFECT OF COLD-EXPOSURE ON TESTICULAR DELTA(5)-3-BETA-HYDROXYSTEROID-DEHYDROGENASE AND 17-BETA-HYDROXYSTEROID-DEHYDROGENASE ACTIVITIES AND PLASMA-LEVELS OF TESTOSTERONE IN TOAD (BUFO-MELANOSTICTUS) IN BREEDINGAND HIBERNATING SEASON - DURATION-DEPENDENT RESPONSE

The purpose of this study was to show the effect of cold exposure on t esticular activities in breeding and hibernating seasons in the toad. Adult male toads were placed in a cold chamber in both breeding and hi bernating seasons for periods of 7, 14 and 21 days. At the time of sac rifice on the 15th and 22nd days, cold-exposed animals showed a decrea se in testicular weight, testicular Delta(5)-3 beta and 17 beta-hydrox ysteroid dehydrogenase activities and low levels of plasma testosteron e both in breeding and hibernating seasons. There was no significant a lteration in the above mentioned steroidogenic enzymes and plasma leve ls of testosterone after 7 days of cold exposure, both in breeding and hibernating seasons in respect to the control animals. The results of our present experiment suggest that environmental cold is an importan t modulator of breeding activities in the male toad. It also indicates that the breeding and hibernating cycle in the toad (seasonal breeder s) may be asynchronous to each other.