The seminal vesicle of the bat (Myotis lucifugus) contained a protein toxic to mice and rabbits but not to bats. This protein was precipitated with ammonium sulphate, non-dialysable, inactivated by papain and relatively heat stable. The lethal action was caused by hypotension due to a general relaxant effect on smooth muscle. Epinephrine only momentarily elevated blood pressure. The toxin had no effect on electrical transmission along the motor-nerve axon and across the neuromuscular junction. Haematocrit values increased significantly after bat seminal vesicle was injected, while a highly significant (P> 0·01) decrease in the proportion of circulating lymphocytes and a highly significant (P>0·01) increase in proportion of circulating heterophils occurred. Isolated mouse duodenum and uterine preparations showed a diminution in contraction frequency and a decrease in muscle tone in the presence of the toxin. This was reversible by washing the toxin from the system.
The hypothesis was proposed that this seminal vesicle protein enters the female bat during copulation, blocks sperm transport, and alters the phagocytic system, thus allowing bat spermatozoa to remain in the female reproductive tract over an extended period of time.
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