Summary. Using an experimental design in which the addition of hypotaurine or epinephrine was staggered through time, evidence was found that suggests these two compounds are working independently and sequentially to stimulate the fertilizing capacity of hamster spermatozoa in vitro. Prior exposure of spermatozoa to hypotaurine is a prerequisite for the action of epinephrine in causing activation and penetration of hamster ova. A definite role for hypotaurine in inducing capacitation of hamster spermatozoa is also demonstrated.
The α-adrenergic antagonist, phentolamine, was more effective in blocking fertilization of hamster ova in vitro than was propranolol, a β-antagonist. This indicates that catecholamines may be working by way of α-adrenergic receptors in causing capacitation of hamster spermatozoa. The failure to block fertilization with phentolamine after epinephrine has exerted its effect implies that epinephrine acts in a hormone-like fashion.