The aim of our in vitro experiments was to examine the role of transcription factor p53 in controlling the basic functions of ovarian cells and their response to hormonal treatments. Porcine ovarian granulosa cells, transfected and non-transfected with a gene construct encoding p53, were cultured with ghrelin and FSH (all at concentrations of 0, 1, 10, or 100 ng/ml). Accumulation of p53, of apoptosis-related (MAP3K5) and proliferation-related (cyclin B1) substances was evaluated by immunocytochemistry. The secretion of progesterone (P(4)), oxytocin (OT), prostaglandin F (PGF), and E (PGE) was measured by RIA. Transfection with the p53 gene construct promoted accumulation of this transcription factor within cells. It also stimulated the expression of a marker of apoptosis (MAP3K5). Over-expression of p53 resulted in reduced accumulation of a marker of proliferation (cyclin B1), P(4), and PGF secretion and increased OT and PGE secretion. Ghrelin, when added alone, did not affect p53 or P(4), but reduced MAP3K5 and increased PGF and PGE secretion. Over-expression of p53 reversed the effect of ghrelin on OT, caused it to be inhibitory to P(4) secretion, but did not modify its action on MAP3K5, PGF, or PGE. FSH promoted the accumulation of p53, MAP3K5, and cyclin B1; these effects were unaffected by p53 transfection. These multiple effects of the p53 gene construct on luteinizing granulosa cells, cultured with and without hormones 1) demonstrate the effects of ghrelin and FSH on porcine ovarian cell apoptosis and secretory activity, 2) confirm the involvement of p53 in promoting apoptosis and inhibiting P(4) secretion in these cells, 3) provide the first evidence that p53 suppress proliferation of ovarian cells, 4) provide the first evidence that p53 is involved in the control of ovarian peptide hormone (OT) and prostaglandin (PGF and PGE) secretion, and 5) suggest that p53 can modulate, but probably not mediate, the effects of ghrelin and FSH on the ovary.