Testicular hyperthermia increases blood flow that maintains aerobic metabolism in rams
G. Rizzoto
A , C. Hall B , J. V. Tyberg B , J. C. Thundathil A , N. A. Caulkett C and J. P. Kastelic A D
A Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.
B Departments of Cardiac Sciences and Physiology and Pharmacology, Libin Cardiovascular Institute of Alberta, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.
C Department of Veterinary Clinical and Diagnostic Sciences, Faculty of Veterinary Medicine, University of Calgary, 3330 Hospital Drive NW, Calgary, AB T2N 4N1, Canada.
D Corresponding author. Email: jpkastel@ucalgary.ca
Reproduction, Fertility and Development 31(4) 683-688 https://doi.org/10.1071/RD17509
Submitted: 1 December 2017 Accepted: 15 October 2018 Published: 19 November 2018
Abstract
There is a paradigm that testicular hyperthermia fails to increase testicular blood flow and that an ensuing hypoxia impairs spermatogenesis. However, in our previous studies, decreases in normal and motile spermatozoa after testicular warming were neither prevented by concurrent hyperoxia nor replicated by hypoxia. The objective of the present study was to determine the effects of increasing testicular temperature on testicular blood flow and O2 delivery and uptake and to detect evidence of anaerobic metabolism. Under general anaesthesia, the testicular temperature of nine crossbred rams was sequentially maintained at ~33°C, 37°C and 40°C (±0.5°C; 45 min per temperature). As testicular temperature increased from 33°C to 40°C there were increases in testicular blood flow (13.2 ± 2.7 vs 17.7 ± 3.2 mL min−1 per 100 g of testes, mean ± s.e.m.; P < 0.05), O2 extraction (31.2 ± 5.0 vs 47.3 ± 3.1%; P < 0.0001) and O2 consumption (0.35 ± 0.04 vs 0.64 ± 0.06 mL min−1 per 100 g of testes; P < 0.0001). There was no evidence of anaerobic metabolism, based on a lack of change in lactate, pH, HCO3− and base excess. In conclusion, these data challenge the paradigm regarding scrotal–testicular thermoregulation, as acute testicular hyperthermia increased blood flow and tended to increase O2 delivery and uptake, with no indication of hypoxia or anaerobic metabolism.
Additional keywords: testis, increased testicular temperature, scrotal–testicular thermoregulation, aerobic metabolism
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