title: Quantitative analysis of the effects of caffeine on sperm motility and cyclic adenosine 3',5'-monophosphate (AMP) phosphodiesterase.
abstract: Caffeine in high concentrations (2 to 6 mM) has been shown to increase sperm motility and metabolism when added to semen. High concentrations of caffeine have also been demonstrated to inhibit cyclic adenosine 3',5'-monophosphate (AMP) phosphodiesterase isolated from sperm. Since cyclic AMP is known to increase sperm motility, some investigators have attributed the stimulatory effect of caffeine on sperm motility to the inhibition of phosphodiesterase. The authors used semen from healthy donors to quantitate the effects of caffeine on sperm motility by turbidimetric analysis and to analyze kinetically the effect of caffeine on phosphodiesterase isolated from sperm preparations. Caffeine (0.012 to 2.0 mM) produced a dose-dependent increase in sperm motility. The ED50 for motility stimulation was 300 microM of caffeine; a significant increase in motility was observed with 60 microM; and maximal stimulation (a threefold increase) occurred with 1 mM. The phosphodiesterase activity of sperm homogenates displayed linear kinetics with a Vmax of 0.5 nmoles/mg of protein per minute and a Km of 125 microM. Caffeine (0.1 to 40 mM) produced a dose-dependent inhibition of sperm phosphodiesterase. Kinetically, caffeine was a mixed inhibitor of sperm phosphodiesterase, displaying a Ki of 1.2 mM. These results suggest that caffeine may stimulate sperm motility by a mechanism other than phosphodiesterase inhibition.
mesh_terms: D015105:3',5'-Cyclic-AMP Phosphodiesterases / Q000037:antagonists & inhibitors*; D002110:Caffeine / Q000494:pharmacology*; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D009994:Osmolar Concentration; D013081:Sperm Motility / Q000187:drug effects*; D013094:Spermatozoa / Q000187:drug effects / Q000201:enzymology*
chemical_list: D002110:Caffeine; D015105:3',5'-Cyclic-AMP Phosphodiesterases