L-Citrulline Single Intravenous Administration Promotes Testicular Blood Flow, Plasma Testosterone, Estradiol, Circulating Citrulline and Serum Nitric Oxide Levels in Male Camels Under Heat Stress at the End of Non-Breeding Season.

This study aimed for the first time to examine the effects of L-citrulline single administration on the camel testicular haemodynamics, morphometry, steroids (estradiol [E2] and testosterone [T]), nitric oxide (NO) and total antioxidant capacity (TAC) under environmental heat stress conditions. For this purpose, 10 adult Maghateer male camels were examined during September 2024 at the end of the non-breeding season. Animals were categorised into a control group (n = 5) and a treated group that received an intravenous dose of L-citrulline (n = 5;155 μmol/kg BW). Testicular length, volume, coloured area, testicular artery (TA) haemodynamics and hormonal profile were examined along the examination (-1, 0, 2, 4, 24, 48, 72, 96 and 120 h after injection). Results represented that no change occurred in testicular length, but the volume was elevated (p < 0.05) from 4 to 96 h after injection with no interaction between treatment and time, but both TA Doppler indices were declined (p < 0.05) at 4-48 h after injection compared to control. Circulating L-citrulline, NO and E2 levels increased 2 h post-injection until 48 h, then all were declined (p < 0.05) again with a lowering pattern of total antioxidant capacity (TAC; p < 0.05), but T took more time to elevate from 4 h until 72 h after injection. L-citrulline could be safe and act as a vasodilator with elevation of steroids (E2 and T), circulating L-citrulline and nitric oxide. This was accompanied by a declination of TAC as early as possible to 48 h. Further studies are needed to show its detailed action on semen quality to be linked with future fertility.