Abstract: Objective：To explore the effect of macamide, an effective extract of maca, on the expression of eNOS in penis cavernosum smooth muscle cells (PCSMC). Methods：The cultured PCSMC was treated with macaamide (100 nmol/L, 100 μmol/L, 100 mmol/L) for 24 h. The expressions of eNOS mRNA and AKT, JNK, P38/MAPK proteins were tested. The PCSMC was also treated with macaamide and SB203580, the inhibitor of P38. The expressions of P38 and eNOS proteins were then tested. Results：After the treatment with macaamide, the expressions of eNOS mRNA and P38/MAPK proteins in PCSMC were significantly increased while the expressions of AKT and JNK proteins were not significantly changed. The expressions of P38 and eNOS proteins were significantly decreased in the PCSMC treated with both macaamide and SB203580, suggesting that SB203580 reversed the upregulation of eNOS induced by macaamide. Conclusions：Macamide can promote the expression of eNOS in PCSMC by activating the P38 pathway.

Key words: Nitric oxide synthase, Penis, Penile erection, Myocytes, smooth muscle, Macamide, Penis cavernosum smooth muscle cells