CALMODULIN CONTENT, CA2-DEPENDENT CALMODULIN-BINDING PROTEINS, AND TESTIS GROWTH - IDENTIFICATION OF CA2+-DEPENDENT CALMODULIN-BINDING PROTEINS IN PRIMARY SPERMATOCYTES()

In contrast with the transient prereplicative increase in calmodulin ( CaM) level observed in proliferative activated cells, postnatal develo pment of rat testis was paralleled by 3 specific rises in CaM. The fir st one occurred between 5 and 10 days, coincident with the appearance and proliferation start of spermatogonia and Sertoli cells. Meiosis ac complishment and spermatid differentiation were paralleled by 2 additi onal rises, at 24 and 32 days, respectively. The plateau phase of test is growth was coincident with the appearance of maturating spermatids and spermatozoa in the germinal epithelium, and with a decrease in CaM content. Testicular DNA:g wet tissue ratio reached the highest level in 15-day-old rats and gradually decreased up to 35 days, when a const ant level was reached. A similar level of Ca2+-CaMBPs was observed in 5- and 20-day-old rat testis. Although all subcellular fractions showe d the ability to bind CaM in a Ca2+-dependent manner, CaM was mainly r ecovered in the nuclear and soluble fractions of adult and immature ra t testis. Several Ca2+-CaMBPs with an apparent M-r of 82, 75, 64, 19, and 14 kD were purified by affinity chromatography from pachytene prim ary spermatocyte nuclear matrix. Ca2+-CaMBPs showing an M-r of 120, 78 , 72, and 66 kD were also purified from the supernatant obtained after DNA and RNA hydrolysis of meiotic nuclei. Major cytosolic Ca2+-CaMBPs of primary spermatocytes showed an M-r of 120, 84, 44, and 39 kD. The functions that these Ca2+-CaMBPs might have during the first meiotic prophase is discussed. (C) 1997 Wiley-Liss, Inc.