Testosterone was measured in the peripheral blood plasma of normal men by radioimmunoassay. The results were analysed to test for the possible existence of a circadian rhythm, for fluctuations superimposed on any such rhythm, and for day-to-day variations.

It has been suggested recently that testosterone secretion by the human testis may be controlled by factors other than luteinizing hormone (LH). In order to re-examine this hypothesis, plasma LH and testosterone concentrations were determined throughout the day in eight studies. A new method of data analysis revealed that the levels of the two hormones were closely related, but that the testicular response to LH was sluggish. These results explain some inconsistencies in the literature. It was demonstrated that average values for LH varied throughout the day, with a morning maximum and an evening minimum. It was also shown that injections of LH releasing hormone in man resulted in an increase in plasma testosterone above control levels. These results are consistent with the concept that LH controls the major changes in testosterone secretion in men. They do not exclude, however, the possible existence of other factors which might affect the peripheral concentration of testosterone, such as changes in testicular blood flow.

No abstract

The composition of epididymal plasma has been described in the boar (Mann, 1964; Crabo, 1965), the bull (Crabo, 1965; Wales, Wallace & White, 1966), the rabbit (Jones & Glover, 1973) and the ram (Scott, Wales, Wallace & White, 1963). In the rat, information on the subject is limited to measurements of ion concentrations (Levine & Marsh, 1971) in fluid collected by micropuncture techniques and to scattered values obtained from post-mortem material (Conchie, Findlay & Levvy, 1959; Dawson & Rowlands, 1959; Marquis & Fritz, 1965; Brooks, Hamilton & Mallek, 1974). The composition of this fluid in any species is important in relation to sperm survival and would seem to be of particular interest in rodents due to its relatively viscous consistency. It would also seem preferable to obtain such fluid from living animals, and with a minimum of contamination. The present paper, therefore, reports on the chemical composition of epididymal plasma obtained from the intact cauda epididymidis of anaesthetized rats. Twelve mature male rats (250 to 350 g) ofthe Wistar strain were anaesthetized with urethane (14% w/v in water; 10\m=.\0 ml/kg intraperitoneally), and the testes were exposed through a scrotal incision. A 23-gauge needle attached to a length of polyethylene tubing (1 mm o.d., 0\ m=. \ 5 mm i.d.) was inserted retrogradely into the ductus deferens, the other end of the tubing being attached to another needle and a syringe. The contents of the cauda epididymidis were collected by aspiration from both ductus deferentes aided by mild electrical stimulation (0\ m=. \ 5 to 5\ m=. \ 0 V) of the smooth muscle of the cauda. Because of the viscous nature of the epididymal fluid in the rat, the caudal contents were expelled gradually over a period of 1 to 2 min and between 30 and 50 \ g=m\ 1 of uncontaminated fluid were obtained.

Summary. Male rats were treated with 5 or 20 mg cyproterone acetate/kg/day or 20 mg cyproterone/rat/day for 1, 2, 3, 4 or 5 weeks. There was some reduction in fertility with both compounds, the maximum effect occurring after 5