OBJECTIVETo investigate the protective effect of L-carnitine (LC) combined with sildenafil on the reproductive endocrine function of male rats with diabetes mellitus (DM).

METHODSA total of 40 male SD rats were randomly divided into five groups, group A taken as normal controls, and groups B, C, D and E made into DM models by injection of streptozotocin at 65 mg/kg. Then the rats in groups A and B were treated with normal saline, C with sildenafil at 5 mg per kg per d, D with LC at 300 mg per kg per d, and E with sildenafil at 5 mg per kg per d plus LC at 300 mg per kg per d, all via gastric gavage for 6 weeks, followed by determination of the levels of testosterone (T), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) in the serum of the rats.

RESULTSAfter 6 weeks of treatment, the T, FSH and LH levels were (25.25 +/- 2.67) nmol/L, (5.78 +/- 0.61) IU/L and (625.21 +/- 43.45) ng/L in group A, (9.63 +/- 1.71) nmol/L, (1.98 +/- 0.42) IU/L and (479.89 +/- 27.62) ng/L in group B, (18.98 +/- 3.07) nmol/L, (5.08 +/- 0.33) IU/L and (586.57 +/- 31.72) ng/L in group C, (16.18 +/- 2.65) nmol/L, (4.63 +/- 0.30) IU/L and (540.78 +/- 25.52) ng/L in group D, and (23.65 +/- 2.66) nmol/L, (5.59 +/- 0.48) IU/L and (621.53 +/- 36. 40) ng/L in group E. The three parameters were significantly lower in B than in the other four groups (P < 0.01), and so were they in C and D than in A and E (P < 0.05), but showed no significant differences either between C and D (P > 0. 05) or between A and E (P > 0.05).

CONCLUSIONSix-week medication of either sildenafil or LC alone could increase the levels of T, FSH and LH in the serum of DM rats, but the combination of the two had an even more obvious increasing effect, which indicates a still better protective effect on the reproductive endocrine function of diabetic male rats.