The Interaction of pH and Cyclic Adenosine 3′5′-Monophosphate on Activation of Motility in Triton X-100 Extracted Bull Sperm1

Abstract

The motility of demembranated bull sperm was found to be governed by the concentrations of cyclic adenosine 3', 5'-monophosphate (cAMP) and Ca2+ at low pH (6.6-7.1), and was less sensitive to these variables at higher pH (7.4-7.8). Although motility was generally found to increase with increasing pH in the range from 6.6 to 7.8, the addition of exogenous cAMP markedly and selectively improved the motility at the lower end of the range (pH 6.6-7.1). In the presence of 10 microM cAMP, low Ca2+ (8.0 X 10(-8) M), and a high concentration of Mg-adenosine 5'-triphosphate (ATP, 8 mM), demembranated sperm at pH 6.8 and 7.1 exhibited swimming similar to that of live ejaculated sperm. At a free Ca2+ concentration of 4.4 X 10(-5) M, the motility was rapidly inhibited at pH 6.8-7.1, whereas at pH 7.4-7.8, the activity was not greatly affected. Since calcium is known to antagonize the cAMP pathway by activating Ca2+-dependent phosphodiesterase and Ca2+-dependent phosphatase, this further supports the idea that cAMP-dependent activation is crucial for motility at low pH. Our results demonstrate that the flagellar axoneme can function normally at relatively acidic pH, and produce vigorous swimming at high levels of ATP. The ATP content of live sperm was measured and found to be high enough (approximately 8 mM) to support the vigorous motility seen at pH 6.6-7.1 in the models.(ABSTRACT TRUNCATED AT 250 WORDS)

Increase in intracellular pH induces phosphorylation of axonemal proteins for activation of flagellar motility in starfish sperm

“…Regardless of the treatment given to sperm before demembranation, the ratio of the reactivated sperm increased in a pH-dependent manner. When sperm showed no motility activation before demembranation (CC treatment), the optimal pH range for reactivation was 7.8 or above, which was almost the same as that reported previously in sea urchin (Gibbons and Gibbons, 1972) and bull (Goltz et al, 1988). However, sperm A. Nakajima and others -1 (right) NH 4 Cl.…”

“…Cyclic AMP (10·mol·l -1 ) improves motility at pH·6.8, from approximately 10% to 80%. This indicates that cAMP is provided by adenylyl cyclase in a pH-dependent manner and plays an important role in motility activation (Goltz et al, 1988). In this case, the pH-dependent motility A. Nakajima and others The band intensities in the CC-treated sperm axoneme (white bars) and in the NH 4 Cl-treated sperm axoneme (black bars) were compared.…”

“…pH-dependent protein phosphorylation activation reflects the pH-dependent increase in cAMP level. Goltz et al (1988) assumed that dynein was phosphorylated in a cAMP-dependent manner, and in that state dynein activity was not limited to an alkaline pH range. However, cAMP did not improve the motility of demembranated starfish sperm in the present experiments.…”

“…It was thought that cAMP-dependent protein phosphorylation is associated with the motility activation through an increase in [pH] i (Brokaw, 1987;Goltz et al, 1988;Carr and Acott, 1989), but little attention has been given to the cAMP-independent phosphorylation induced by the [pH] i increase. Whether the increasing [pH] i induces the phosphorylation of dynein component(s) or other axonemal proteins independently of cAMP remains unknown.…”

“…It is thought that cAMP-dependent protein phosphorylation is associated with motility activation through increased [pH] i (Brokaw, 1987;Goltz et al, 1988;Carr and Acott, 1989), but little attention has been given to the cAMP-independent phosphorylation induced by the increased [pH] i . According to Carr and Acott (1989), two proteins are phosphorylated in intact bull sperm during motility activation induced by an increase in [pH] i , and the phosphorylation is probably not due to changes in cAMP levels.…”