Induction of Motility in Immature Bovine Spermatozoa by Cyclic AMP Phosphodiesterase Inhibitors and Seminal Plasma

Motility can be induced in immature spermatozoa from the bovine caput epididymidis by cyclic 3′,5′-adenosine monophosphate (cAMP) phosphodiesterase inhibitors (PDIs) and bovine seminal plasma. PDIs alone indicate flagellar activity without forward progression. Initiation of maximal movement without forward progression requires the presence of high levels of PDIs and is characterized by a distinct lag phase, the duration of which depends on the nature and concentration of the inhibitor. With theophylline (10 mM), for example, the cells reach maximal activity after 12–13 min. That theophylline owes its efficacy to an inhibition of phosphodiesterase is indicated by the fact that cyclic AMP levels increase 3- to 4-fold after the addition of theophylline and reach a maximal level (700 pmoles/109 sperm) several minutes before peak flagellar activity. The same time lag occurs with the PDIs papaverine (100 μM), SQ80002 (50 μM), and SQ20006 (10 mM) but with the cyclic AMP derivative, dibutyryl cyclic AMP (5 mM), the lag phase is considerably longer (40 min) and the peak stimulation (5 percent) is smaller than with PDIs. Adding 10 mM glucose shortens the lag phase and increases the maximal response to Bt2 cAMP (5 mM), SQ80002 (25 mM), and theophylline (25 mM). Seminal plasma alone has no effect on either motility or intracellular cAMP levels but when 8 percent seminal plasma (optimum level) is added to 25 mM theophylline, 50 percent of the caput sperm show flagellar activity, and 80 percent of these move forward in a rotating fashion at about 58 μm/sec. When 4 percent bovine serum albumin (BSA) is added to 25 mM theophylline 40 percent of the caput sperm become motile, but less than one-half of these cells (20 percent of total) move forward in a circular kind of motion which diminishes after 10 min and is lost after 35 min. These data support the view (Hoskins et al., 1974) that an increase in the intrasperm level of cAMP is an important, but not the sole, factor in the normal development of sperm motility in the bovine epididymis.