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J. C. BOURSNELL and E. J. BUTLER

Summary.

A method of studying boar seminal gel has been devised which enables investigation to be made on the chemical and physical properties of the gel formed in vitro from the bulbo-urethral (Cowper's) gland mucin and either vesicular secretion or seminal plasma. The majority of the haemagglutinin (protein H) in boar vesicular secretion combines with the mucin to form the gel. The content of Zn, Mg and citrate of the natural gel is less (often 0·9 × ) than that of the seminal plasma; this ratio also applies to the Kjeldahl N material imbibed in vitro from seminal plasma or vesicular secretion (as distinct from the N contributed by the mucin). The imbibed aqueous solution of seminal plasma or vesicular secretion can be defined as `interstitial' in that its components are diffusible from the gel matrix into buffer. Part of the interstitial water (possibly as much as 10%) is `bound' physicochemically to the gel matrix and is unavailable for solvation of the seminal fluid components.

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J. C. BOURSNELL, P. A. BRIGGS, U. LAVON and E. J. BUTLER

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.

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J. C. BOURSNELL, P. A. BRIGGS, U. LAVON and E. J. BUTLER

Summary.

Gel-filtration and dialysis studies on the state of zinc in boar seminal plasma and vesicular secretion strongly suggest that the zinc is partitioned between two or more ligands of which the most likely are proteins and citrate. This partition is very sensitive to changes in pH and buffer composition and an increasing proportion of the zinc is precipitated at pH values above 7. No firmly bound protein-zinc complex was found which could account for the close correlation between the zinc and protein nitrogen contents previously observed for these fluids.

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J. C. BOURSNELL, S. BARONOS, P. A. BRIGGS and E. J. BUTLER

Summary.

Forty-five samples of seminal plasma obtained from eight boars and seventeen samples of vesicular secretion collected from individual boars had mean zinc contents of 22·7 and 137·4 μg/ml, respectively. It was concluded that most of the zinc present in the seminal plasma of the boar is derived from the vesicular secretion.

The mean concentrations of the organic constituents studied were:

Seminal plasma: total nitrogen 4·42 mg/ml (non-dialysable 88·7%), citrate 1·28 mg/ml.

Vesicular secretion: total nitrogen 15·1 mg/ml (non-dialysable 93·9%), citrate 6·07 mg/ml, fructose 0·557 mg/ml, galactose 0·092 mg/ml.

In both seminal plasma and vesicular secretion, the concentration of zinc was positively correlated with that of total and non-dialysable nitrogen and citrate. The correlation with nitrogenous substances was particularly strong in the seminal plasma of individual animals and there was evidence from the partial correlation coefficients that these associations were independent of the zinc-citrate relationship. However, fructose and galactose which do not have an appreciable affinity for zinc under physiological conditions also showed significant positive correlations with zinc (in vesicular secretion) and most of the organic constituents were interrelated in this way, indicating that in such data the influence of chemical combination may be masked by that of other factors which regulate the composition of these fluids.