set at the maximum speed (5 x 1O s at 0C). The receptor preparation was suspended at a concentration of 2 g in 10 ml of assay buffer (0.05 M, Tris-buffer, pH 7.5, containing 0.1 % BSA, 5 mM MgCI2 and 0.1 M sucrose).The testicular receptors were obtained from immature (21-day-old) Holtzman rats (Reichert & Abou-Issa, 1977). The receptor preparations were suspended at a concentration of I g in 10 ml in the assay buffer.Human FSH (hFSH-13) was iodinated by the chloramine-T method (Reichert & Bhalla, 1974) with a specific activity of about 15 tCi yg-'.Binding studies were performed using labelled hFSH (5 ng hFSH in 50 d l assay buffer) in the presence of serial dilutions of unlabelled FSH (I -250 ng) with 50 mg of testicular receptor in 500 gl of assay buffer. The total reaction volume was made up to I ml by addition of assay buffer. The tubes were then incubated in a metabolic shaker at 37°C for 2 h. Incubation was terminated by addition of 2 ml of chilled buffer. The tubes were then centrifuged at 1,500g for 15 min. The supernatant was discarded by decantation and the tubes were drained and counted in the well type gamma-counter. The non-specific binding was determined in presence of a 1000-fold excess of oFSH (NIH-FSH-S-16).

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Adenosine trio-phosphate is the main energy source available for the spermatozoa propulsion. It is well established that any alteration of ATP pool either directly or indirectly affects sperm motility (Mitchell et al. -1976). Human spermatozoa contain a hydrolysing enzyme, adenosine trio-phosphatase (ATPase) which is stimulated by sodium and potassium ions in presence of magnesium ions (Durr et al. -1972). This