Effect of Short‐Term Scrotal Hyperthermia on Spermatological Parameters, Testicular Blood Flow and Gonadal Tissue in Dogs

Abstract

The objective was to assess the effect of a short-term scrotal hyperthermia in dogs on quantitative and qualitative ejaculate parameters, testicular blood flow and testicular and epididymal histology. After a control period, the scrotum of seven normospermic adult beagle dogs was insulated with a self-made suspensory for 48 h. Nine weeks later, two animals were castrated, while in five animals, scrotal hyperthermia was repeated. Dogs were castrated either 10 or 40 days thereafter. In each phase of scrotal insulation, average scrotal surface temperature increased by 3.0°C. Semen was collected twice weekly throughout the experiment. Total sperm count did not change after the first hyperthermia, but it slightly decreased after the second (p < 0.05). Profiles of sperm morphology and velocity parameters (CASA) rather indicated subtle physiological variations in sperm quality than effects of a local heat stress. Chromatin stability of ejaculated spermatozoa as indicated by SCSA remained constant throughout the experiment. Perfusion characteristics of the gonads, that is, systolic peak velocity, pulsatility and resistance index at the marginal location of the testicular artery, did not change due to hyperthermia (p > 0.05). Histological examination of excised testes and epididymides for apoptotic (TUNEL and activated caspase-3) and proliferating cells (Ki-67 antigen) indicated only marginal effects of scrotal insulation on tissue morphology. In conclusion, a mild short-term scrotal hyperthermia in dogs does not cause substantial changes in sperm quantity and quality. In contrast to other species, canine testes and epididymides may have a higher competence to compensate such thermal stress.

Bax and Bcl‐2 are involved in the apoptosis induced by local testicular heating in the boar testis

“…Our results showed that the local testicular heating caused a significant increase in the TUNEL‐positive cell numbers of round and elongated spermatids. Our results agree with prior reports (Lue et al., ; Yamamoto et al., ; Oldereid et al., ; Hikim et al., ; Zhang et al., , ; Merico et al., ; Jia et al., ; Paul et al., ; Kanter et al., ; Liang et al., ; Henning et al., ), in which heat stress resulted in the apoptosis of germ cells. But a little different from the report by Lue et al.…”

“…In this study, a self‐made thermo‐controlled 42°C blanket was used in the local testicular heating group. Recently, several studies in a few animals suggested that testes exposed to above body temperature (40–43°C) cause apoptosis in germ cells, including mice (Merico et al., ; Paul, Teng, & Saunders, ; Liang, Dong, Zhao, & Li, ), rats (Yamamoto et al., ; Hikim et al., ; Jia et al., ), dogs (Henning et al., ) and monkeys (Zhang et al., , ). Several studies also confirmed that exposing testes to above body temperature affects normal spermatogenesis, sperm fertility and male fertility (Gnay et al., ; Ikeda et al., ; Gau et al., ; Li et al., ; Guo et al., ; Salces‐Ortiz et al., ; Xun et al., ).…”

Clinical utility of sperm DNA fragmentation testing: practice recommendations based on clinical scenarios

“…While several theories have been proposed to explain the deleterious effects of varicocele on testicular function, testicular hyperthermia is perhaps the most commonly accepted one. It has long been observed that minor changes in testicular temperature can affect spermatogenesis (52) as many of the enzymes responsible for DNA synthesis in the testis are temperature dependent (53), mainly favoring temperatures lower than 98.2±0.72 °F (normal body temperature). The anatomic position of the testis in the scrotal sac together with the countercurrent cooling mechanism provided by the pampiniform plexus of veins are responsible regulating testicular temperature (54).…”

Effect of local scrotal heating on the expression of tight junction‐associated molecule Occludin in boar testes

“…Scrotal heating can cause temporary or permanent infertility, such as occupationally (bakers, welders, foundry workers) or through submerging in a hot water bath (Mieusset & Bujan, 1995;Thonneau, Bujan, Multigner, & Mieusset, 1998). Several studies have also illustrated that the elevation of testicular temperature affects the spermatogenesis and semen quality in most mammals, including mouse (Paul et al, 2009), dogs (Henning et al, 2014), monkeys (Zhang et al, 2004) and bulls as well (Ax, Gilbert, & Shook, 1987). Furthermore, Cai et al (2011) demonstrated that scrotal heating usually affects spermatogenesis by altering the expression of tight junctions (TJs) molecules.…”