Opalescence and precipitation of boar seminal plasma proteins, specifically promoted by zinc, have been shown to be due to a zinc-precipitable protein (ZPP). The properties of this purified protein cannot be distinguished from those of the seminal haemagglutinin and their identity is postulated. The response of seminal plasma opalescence to low temperature is especially marked between 14\s=deg\Cand 6\s=deg\C.This is notably similar to the already recorded response of sperm survival to cooling. When semen is cooled to 4\s=deg\C,ZPP, accompanied by zinc, is absorbed by spermatozoa.

Summary. Ultrafiltration studies strengthen the suggestion that zinc in boar seminal plasma and vesicular secretion is partitioned between high and low molecular weight ligands. Studies employing graded ethanol precipitation of seminal plasma proteins failed to reveal the presence of a zinc-rich protein.

Summary. Using the method of radio-activation analysis, zinc was determined in the testes of rats varying in age from 7 to 58 days.During the first month of life the zinc concentration remained fairly constant (120 ng/mg testicular dry weight), and no decrease in testicular zinc concentration occurred at the time when the rat testis first acquires its sensitivity to the necrotic action of cadmium (approximately 9 days of life). This is of special significance in view of the fact that parenterally administered zinc salts counteract the action of cadmium.During the second month of life, the concentration of testicular zinc increased considerably. This increase, which coincides roughly with the time when spermatids are transformed into spermatozoa, may well be related to the formation of intracellular zinc-metalloproteins, including certain zinc-containing enzymes in spermatozoa.

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The temperature-dependent opalescence caused by the presence of a zinc-precipitable protein (ZPP) in boar seminal plasma has been shown to be pH-dependent.The considerable pH increase to which boar seminal plasma is subject on exposure to air is attributed to loss of CO2 from a system with a notable paucity of titratable groups in the physiological range pH 7 to 9. This markedly affects the temperature-dependent opalescence.The ZPP has been purified and the temperature-dependent opalescence of this material can be demonstrated only within a narrow range of zinc concentration in the absence of other possible ligands present in whole seminal plasma.