Spermatogenesis and testicular tumours in ageing dogs

Spermatogenesis was examined in testes from 74 dogs of various breeds witho ut clinically detected testicular disease. A modified Johnsen score system was used to determine whether spermatogenesis deteriorates with ageing. The diameter of seminiferous tubules was measured in dogs without testicular d isease to examine other possible effects of ageing on tubular performance. There appeared to be no relation between age and these variables. The influ ence of testicular tumours on spermatogenesis was also investigated in both affected and unaffected testes. The testes of 28 dogs with clinically palp able rumours and 21 dogs with clinically non-palpable tumours were investig ated. In cases of unilateral occurrence of a tumour, impairment of spermato genesis was observed only in the affected testis of dogs with clinically de tected rumours. Bilateral occurrence of rumours, whether detected clinicall y or non-clinically, was associated with severe impairment of spermatogenes is. The prevalence of tumours increased during ageing. Eighty-six per cent of the clinically detected and 57% of the non-clinically detected tumours w ere found in old dogs. Multiple types of tumour and bilateral occurrence we re very common. Seminomas and Leydig cell tumours were more frequent than S ertoli cell tumours. It was concluded that spermatogenesis per se did not d ecrease during ageing in dogs but the occurrence of testicular tumours incr eased with ageing and affected spermatogenesis significantly, as reflected by a lower Johnsen score.