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Testicular tissue and blood samples (V. spermatica interna) were taken from 32 boars during castration. The animals were different age groups. Against this background, studies were conducted into the correlations between testicular and plasma testosterone, on the one hand, and the amount of interstitial cells of Leydig in testicular tissue as well as the latters' cell nuclei volumes, on the other. The results seemed to support the conclusion that any age-dependent increase of testicular and plasma testosterone concentrations was caused unambigously by an absolute increase in volume of androgenic testicular tissue, in concomitance with testicular growth, in other words, by rise in the total number of interstitial cells of Leydig.

A clearly morphokinetic effect was recorded from the parts of the hypothalamo-adenohypophyseo-gonadal axis in boars that had been treated with chloromadinone acetate (CAP). Luteinising hormone release is inhibited by CAP, which is reflected in an increase of luteinising hormone cells in their storage form. This leads to statistically significant decline in androgenic testicular tissue percentage and in the cell nucleus volumes of Leydig's cells. Excessive weight decrease of the testicle is caused primarily by some 60 per cent reduction in tube length. The neurons of the tested hypothalamic nuclear region, that is the nucleus praeopticus medialis, have shown that in treated animals cell nucleus volumes were significantly depressed.

Morphokinetic effects caused in parts of the hypothalamic adenohypophyseogonadal axis of boars by treatment, using No. 547 steroid test substance (ZIMET, Jena) were to some extent identical with those resulting from analogous CAP application (inhibition of testicular androgen producers, anterior lobe of the pituitary gland, nucleus praeopticus medialis) or those following analogous norgestrel treatment (testes weight, tubule length). The findings recorded were largely attributed to the androgenic properties of No. 547 steroid test substance.

Steroid test substance 547 and Norgestrel were used in a combination treatment of parts of the hypothalamo-adenohypophyseo-gonadal axis of boars. The quantifiable parameters of the morphokinetic effect thus produced (cell nucleus volumes of Nucleus praeopticus medialis hypothalami and its neurons as well as those of Leydig's cells testicle weight, length and diameter of tube, percentage of Leydig's cells, testicle weight, length and diameter of tube, percentage of Leydig's cells) did not differ significantly from the findings obtained from boars treated with Norgestrel only (cf. Dorst and co-workder, 1978). The same combination treatment, however, differed from exclusive Norgestrel treatment by causing the occurrence of socalled castration cells, which led to the assumption of an anti-androgenic effect of such combination treatment.

Close, statistically fully secured correlations were found to exist in boars, aged between four and four-a-half as well as seven and nine months, between the testosterone content in the blood of the V. spermatica interna, on the one hand, and morphometric parameters essential to quantitative sperm production, on the other (testicular volume, volume of germinativum, overall length of tubules, diameter of tubules, and cell density of the germinal epithelium).