Effect of genistein on amylase release and protein tyrosine phosphorylation in parotid acinar cells

Effect of endocrine disruptors on the ratio of X and Y chromosome-bearing live spermatozoa

Although equal numbers of X and Y spermatozoa are produced during spermatogenesis, the sex chromosome ratio in ejaculated spermatozoa can be altered by exposure to endocrine-disrupting chemicals (EDCs), which can be reflected by altered sex ratios at birth. Here, we hypothesized EDCs affect sperm functions and viability of X and Y chromosome-bearing human spermatozoa. After exposure to genistein (Gen), bisphenol A (BPA), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), dibromochloropropane (DBCP), and diazinon (Diaz), we evaluated motility, viability, capacitation, and differential viability of X and Y spermatozoa. All EDCs tested altered sperm viability, motility, and capacitation. Interestingly, the Y/X ratio of live spermatozoa was significantly lower in sperm treated with TCDD, DBCP, and Diaz than control spermatozoa. Our results suggest that some of EDCs have larger effects on the viability of Y spermatozoa than X spermatozoa, implicating that a reduction in Y sperm viability may result in a female-biased sex ratio of offspring at birth.

Staurosporine-inhibitable protein kinase activity associated with secretory granule membranes isolated from rat submandibular gland cells

Protein kinases, such as protein kinase C, have been shown to be associated with secretory granules and to regulate the event of exocytosis in various tissues including parotid salivary acinar cells. However, in submandibular acinar cells that play an important role in the secretion of proteins into the oral cavity, kinase activity on the granule membrane has not been explored. Therefore, in the present study, we isolated the secretory granules from rat submandibular acinar cells and investigated the localisation of protein kinases on the granule membrane. Initially, we isolated and purified secretory granules from rat submandibular acinar cells. Addition of [gamma-32P] ATP to granule-membrane lysate phosphorylated the granule-membrane-associated 26, 32, 55 and 58kDa proteins, suggesting the presence of endogenous kinase activity on the membrane. Moreover, the phosphorylation of 26 and 32kDa proteins was inhibited by staurosporine and K252a, both non-specific protein kinase C inhibitors. However, the phosphorylation of 26 and 32kDa proteins was not inhibited by other protein kinase C inhibitors, such as calphostin C, GF109203X and chelerythrine, indicating that protein kinase C was not responsible for the phosphorylation. In addition, H-89, ML-9, KN-62 and genistein did not appear to inhibit this phosphorylation, indicating that protein kinase A, myosin light chain kinase (MLCK), Ca2+/calmodulin-dependent protein kinase II (CAMKII) and tyrosine kinase were not involved in the phosphorylation of 26 and 32kDa proteins. Moreover, Ca2+ had no effect on the kinase activity. Therefore, our results suggest that an unidentified, staurosporine-inhibitable protein kinase activity is associated with the secretory granule membrane of rat submandibular acinar cells.

Enhancement of Ca2+-induced noradrenaline release by vanadate in PC12 cells: possible involvement of tyrosine phosphorylation

Tyrosine phosphorylation has been shown to participate in the signal cascade after receptor stimulation with neurotransmitters and neurotrophins. However, the role of tyrosine phosphorylation in the process(es) of neurotransmitter release has not been well established. The effects of orthovanadate (Na3VO4), an inhibitor of protein-tyrosine phosphatases, on cytosolic free Ca2+ concentrations ([Ca2+]i), phosphotyrosine accumulation and noradrenaline (NA) release in neurosecretory PC12 cells were investigated. Addition of Na3VO4 enhanced ionomycin-stimulated [3H]NA release in a concentration-dependent manner, although Na3VO4 alone had no effect. Na3VO4 also enhanced [3H]NA release induced by P2 receptor stimulation with adenosine 5'-O-(3-thiotriphosphate) (ATPgammaS) or by depolarization with 50 mM KCl, which stimulated a [Ca2+]i increase. A cell permeable inhibitor of protein-tyrosine phosphatases, L-p-bromotetramisole oxalate, at 0.3 mM enhanced ionomycin-stimulated [3H]NA release, although pervanadate had no effect. Addition of 5 mM Na3VO4 stimulated phosphotyrosine accumulation in several protein bands such as p130cas, but did not increase [Ca2+]i in PC12 cells. These findings suggest that the tyrosine phosphorylation pathway regulates Ca2+-stimulated NA release without changes of [Ca2+]i in PC12 cells.