The level of endothelin-like immunoreactivity in seminal fluid correlates positively with semen volume and negatively with plasma gonadotrophin levels.
OBJECTIVE
The newly discovered vasoactive peptides, endothelin 1, 2 and 3, and their receptors are widely distributed in various non-vascular tissues. Recent studies have suggested the presence, as well as possible regulatory roles, of endothelins at several levels of the pituitary-gonadal axis. We determined the level of endothelin-like immunoreactivity in the seminal fluid and examined its possible correlation with routine semen parameters or plasma levels of FSH, LH or testosterone.


METHODS
Prospective study in a tertiary care centre.


METHODS
Ninety-one men attending infertility clinics for male factor, female factor or both.


METHODS
Endothelin-like immunoreactivity was determined in seminal fluid using two radioimunoassays, ET1-21 that measures endothelin and ET-1,2 that measures both endothelin and big endothelin. In addition, the levels of FSH, LH and testosterone as well as routine semen parameters were determined.


RESULTS
Sperm density ranged from 0 to 315 x 10(6) with a mean (+/- SD) of 28.5 x 10(6) (+/- 48 x 10(6)) sperm/ml and the percentage of motile sperm ranged from 0 to 85% with a mean of 16% (+/- 20.5%). Mean levels of FSH (n = 33), LH (n = 35) and testosterone (n = 35) were 6.4 +/- 4.9 IU/l, 3.5 +/- 2.8 IU/l and 21 +/- 9.4 nmol/l, respectively. Mean ET1-21 level (n = 91) was 81 +/- 16.5 pmol/l, and mean ET-1,2 level (n = 33) was 630.5 +/- 143 pmol/l. There were significant correlations between the levels of ET1-21 and ET-1,2 (r = 0.37, P = 0.04), ET1-21 and FSH (r = -0.5, P = 0.006), ET1-21 and LH (r = -0.46, P = 0.01), and ET1-21 level and semen volume (r = 0.23, P = 0.03). Mean level of ET1-21 or ET-1,2 was significantly lower in patients treated empirically with clomiphene citrate or gonadotrophins (n = 34) compared to untreated (n = 52) patients (P = 0.04).


CONCLUSIONS
We conclude that in human seminal fluid (1) endothelin-like immunoreactivity that is specific for active endothelin (ET1-21) represents about 13% of the total immunoreactivity; (2) inactive big endothelin or its N-terminal derivative(s) may account for most of the immunoreactivity; (3) the production/secretion of endothelin may be inhibited by LH and/or FSH; and (4) endothelin level correlates positively with seminal fluid volume.
Hammami
M M
MM
Department of Medicine, King Faisal Specialist Hospital, Riyadh, Saudi Arabia.
Haq
A
A
AlSedairy
S
S
D016232:Endothelins / Q000032:analysis*; D005640:Follicle Stimulating Hormone / Q000097:blood; D006065:Gonadotropins, Pituitary / Q000097:blood*; D006801:Humans; D007248:Infertility, Male / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D011446:Prospective Studies; D011863:Radioimmunoassay; D012661:Semen / Q000737:chemistry*; D013076:Sperm Count; D013081:Sperm Motility / Q000502:physiology
D016232:Endothelins; D006065:Gonadotropins, Pituitary; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone