The specific activities of protein kinase C (PKC) and protein tyrosine kinase (PTK) were determined in the decidualized uterine tissue of pseudopregnant rat on day 5 of decidualization. We found that the activity of the cytosolic PKC was significantly lower in decidualized uterine tissue as compared with that of the controlateral untreated uterine tissues (1.5 +/- 1.4 versus 57.5 +/- 4.1 pmol 32P/min/mg, P < 0.001), while the PKC activity in particulate fraction was not significantly different (124.8 +/- 14.5 versus 236.8 +/- 88.6 pmol 32P/min/mg) concerning protein concentration. The reduced expression of the cytosolic PKC activity was observed on all five individual rats. In contrast, the decidualized uterine tissue showed similar cytosolic PTK activity as compared with the controlateral untreated uterine tissues (20.1 +/- 3.0 versus 20.6 +/- 3.2 pmol 32P/min/mg protein), and similar in particulate PTK activity (42.5 +/- 9.0 versus 36.8 +/- 5.1 pmol 32P/min/g protein). These results indicate that cytosolic PKC activity may be involved in modulation of decidual growth.
