SEASONAL AND EXPERIMENTAL REACTIVATION OF LEYDIG-CELLS OF THE BAT TADARIDA-BRASILIENSIS

The Leydig cells of the bat Tadarida brasiliensis, exhibit two well-de fined periods of secretory activity that are intimately associated to the bat reproductive cycle. During the breeding season (August-Septemb er, late Winter and early Spring in the southern hemisphere), the inte rstitial tissue contains hypertrophic Leydig cells characterized ultra structurally by the presence of pleomorphic mitochondria, depletion of lipid droplets, proliferation of membranes of agranular endoplasmic r eticulum (AER) and enlargement of the Golgi complexes. By contrast, fr om Spring to Fall concurrent with regression of seminiferous tubules, the Leydig cells acquire a quiescent appearance with reduction in size and volume of AER membranes, atrophy of the Golgi complex and a massi ve storage of lipid droplets. The changes occurring in Leydig cells du ring the breeding season can be duplicated experimentally in non-breed ing bats with exogenous stimulation with hCG. The gonadotropic treatme nt induces rapid changes in both interstitial cells and seminiferous t ubules. The latter present evident signs of reactivation including pro liferation of the spermatogenic cell line, permeation of the tubular l umen and depletion of lipid droplets. The Leydig cells display similar features to those found in the bat during the mating season at the pe ak of secretory activity. The bat T. brasiliensis is an excellent mode l to correlate the morphological organization of the Leydig cells with either seasonal fluctuations of its secretory activity or after exper imental stimulation with gonadotropins.