Prostaglandin F2 alpha (PGF2 alpha) stimulates protein synthesis of skeletal and smooth muscle cells in culture and is elevated in the heart during compensatory growth. We hypothesized that PGF2 alpha stimulates hypertrophic growth of neonatal rat cardiac myocytes. Prostaglandin F2 alpha increased [3H]phenylalanine incorporation by cultured ventricular myocytes in a dose-dependent manner (EC50 = 11 nM), suggesting action through a PGF-specific receptor. Semiquantitative reverse transcriptase polymerase chain reaction revealed that PGF receptor mRNA is expressed in ventricular myocytes > A7R5 vascular smooth muscle cells >> cardiac fibroblast-like cells. The protein content of cardiomyocyte cultures was increased by 10 nM PGF2 alpha and 11 beta-PGF2 alpha but was unchanged by 10 nM PGD2, PGE2, PGF1 alpha, carbaprostacyclin, U-46619, or 12- or 15-hydroxyeicosatrienoic acid. Stimulation of myofibrillar gene expression by PGF2 alpha was demonstrated by Northern and Western blot analysis for myosin light chain-2 (MLC-2) and by transient transfection experiments with MLC-2 luciferase expression plasmids. In addition, myofibrillogenesis was increased by PGF2 alpha as assessed by immunocytochemical staining with MLC-2 antisera. Prostaglandin F2 alpha did not affect myocyte proliferation or [3H]thymidine incorporation, thus myocyte growth occurred by hypertrophy. Proliferative and hypertrophic growth of cardiac fibroblast-like cells were unaffected by PGF2 alpha. We conclude that PFG2 alpha stimulates hypertrophic growth of neonatal rat ventricular myocytes in culture and speculate that PGF2 alpha plays a role in myocardial adaptation to chronic hypertrophic stimuli, recovery from injury, and cardiac ontogeny.