Ion transport and metabolism in slices of guinea-pig seminal-vesicle mucosa.

Lardy & Phillips (1943), and Blackshaw (1953) found that bull and ram spermatozoa show optimum motility in vitro only when at least 5-10 mM-K' ions are present in the rpedium. Potassium also stimulates the metabolism of spermatozoa, and Dott & Walton (1956) have shown that both glycolysis and respiration are needed for maximum motility. Potassium is therefore essential for the motility and metabolism of spermatozoa. It is present in the natural milieu for spermatozoa on ejaculation, namely seminal plasma, which is elaborated mainly by the seminal vesicles in the rat, guinea pig and bull (see Mann, 1954). As a preliminary to the study of the secretion of ions in seminal plasma, Breuer & Whittam (1957) tried to find out how the high potassium concentration was maintained in slices of seminal-vesicle mucosa of the guinea pig. They showed that anaerobiosis had little effect on the tissue sodium and potassium concentrations during incubation at 370, but that inhibitors of glycolysis anaerobically or of respiration aerobically caused a loss of potassium and a gain of sodium. Metabolic energy from either respiration or anaerobic glycolysis was therefore needed to support the concentration gradients of sodium and potassium, which they suggested may depend upon a supply of adenosine triphosphate, the formation of which is common to both metabolic pathways. The electrical potential difference across the cell membranes is not known and it is not possible therefore to decide whether both potassium and sodium are actively transported. Thus the intracellular potassium concentration could be maintained either by a primnary active transport of potassium or by a primary active outward movement of sodium, which would generate a potential difference and cause a passive inward movement of potassium. The present work has shown that, whether sodium or potassium or both ions are actively transported, there is a correlation between the retention of potassium and the exclusion of sodium, and the concentration of easily hydrolysable phosphate. Other experiments are described which show that a reduction in the sodium concentration of the medium caused a roughly proportional fall in the tissue sodium concentration, without the tissue potassium concentration being affected. Under these conditions the intracellular potassium is probably retained passively by nondiffusible anions.