POLY(ADPRIBOSYL)ATION SYSTEM IN RAT GERMINAL CELLS AT DIFFERENT STAGES OF DIFFERENTIATION

In order to study the possible functional relationship between poly(AD P-ribosyl)ation and spermatogenesis, the three main germinal cell type s have been isolated and characterized as haploid spermatids and diplo id and tetraploid spermatocytes, Purified germinal cell populations an d rats of different age were used for activity-, immuno-, and Northern blot experiments, to determine at which level poly(ADPR) polymerase ( PARP) is regulated at various stages of spermatogenesis. Poly(ADPR)gly cohydrolase (PARG) activity was also determined, as was the subcellula r distribution of both PARP and PARG; enzymes. The results show that t he maximum of both PARP amount and PARP activity can be detected on te traploid spermatocytes which undergo meiotic division, whereas PARG ac tivity does not differ in germinal cells; the cytoplasmic form of this enzyme is prevalent in testis. Moreover, a difference in timing was o bserved in maximal level between PARP expression, determined on testis from 60-day-old rats, and PARP activity, detected on testis from 30-d ay-old animals. It seems that different mechanisms modulate the poly(A DPribosyl)ation system during spermatogenesis. Regulation of the poly( ADPribose) turnover, variations of PARP amount, as well as changes of PARP transcription level, seem to accompany germinal cell differentiat ion, possibly being implicated in DNA replication, repair, and transcr iption. (C) 1996 Academic Press, Inc.