TY - JOUR
T1 - Lamprey GnRH-III acts on its putative receptor via nitric oxide to release follicle-stimulating hormone specifically
AU - Yu, W. H.
AU - Karanth, S.
AU - Mastronardi, C. A.
AU - Sealfon, S.
AU - Dean, C.
AU - Dees, W. L.
AU - McCann, S. M.
PY - 2002/10
Y1 - 2002/10
N2 - Lamprey gonadotropin-releasing hormone-III (I-GnRH-III), the putative follicle-stimulating hormone (FSH)-releasing factor (FSHRF), exerts a preferential FSH-releasing activity in rats both in vitro and in vivo. To test the hypothesis that I-GnRH-III acts on its own receptors to stimulate gonadotropin release, the functional activity of this peptide at mammalian (m) leutinizing hormone (LH)RH receptors transfected to COS cells was tested. I-GnRH-III activated m-LHRH receptors only at a minimal effective concentration (MEC) of 10-6 M, whereas m-LHRH was active at a MEC of 10-9 M, at least 1,000 times less than that required for I-GnRH-III. In 4-day monolayer cultured cells, I-GnRH-III was similarly extremely weak in releasing either LH or FSH, and, in fact, it released LH at a lower concentration (10-7 M) than that required for FSH release (10-6 M). In this assay, m-LHRH released both FSH and LH significantly at the lowest concentration tested (10-10 M). On the other hand, I-GnRH-III had a high potency to selectively release FSH and not LH from hemipituitaries of male rats. The results suggest that the cultured cells were devoid of FSHRF receptors, thereby resulting in a pattern of FSH and LH release caused by the LHRH receptor. On the other hand, the putative FSH-releasing factor receptor accounts for the selective FSH release by I-GnRH-III when tested on hemipituitaries. Removal of calcium from the medium plus the addition of EGTA, a calcium chelator, suppressed the release of gonadotropins induced by either I-GnRH-III or LHRH, indicating that calcium is required for the action of either peptide. Previous results showed that sodium nitroprusside, a releaser of nitric oxide (NO), causes the release of both FSH and LH from hemipituitaries incubated in vitro. In the present experiments, a competitive inhibitor of NO synthase, L-NG-monomethyl-Larginine (300 μM) blocked the action of I-GnRH-III or partially purified FSHRF. The results indicate that I-GnRH-III and FSHRF act on putative FSHRF receptors by a calcium-dependent NO pathway.
AB - Lamprey gonadotropin-releasing hormone-III (I-GnRH-III), the putative follicle-stimulating hormone (FSH)-releasing factor (FSHRF), exerts a preferential FSH-releasing activity in rats both in vitro and in vivo. To test the hypothesis that I-GnRH-III acts on its own receptors to stimulate gonadotropin release, the functional activity of this peptide at mammalian (m) leutinizing hormone (LH)RH receptors transfected to COS cells was tested. I-GnRH-III activated m-LHRH receptors only at a minimal effective concentration (MEC) of 10-6 M, whereas m-LHRH was active at a MEC of 10-9 M, at least 1,000 times less than that required for I-GnRH-III. In 4-day monolayer cultured cells, I-GnRH-III was similarly extremely weak in releasing either LH or FSH, and, in fact, it released LH at a lower concentration (10-7 M) than that required for FSH release (10-6 M). In this assay, m-LHRH released both FSH and LH significantly at the lowest concentration tested (10-10 M). On the other hand, I-GnRH-III had a high potency to selectively release FSH and not LH from hemipituitaries of male rats. The results suggest that the cultured cells were devoid of FSHRF receptors, thereby resulting in a pattern of FSH and LH release caused by the LHRH receptor. On the other hand, the putative FSH-releasing factor receptor accounts for the selective FSH release by I-GnRH-III when tested on hemipituitaries. Removal of calcium from the medium plus the addition of EGTA, a calcium chelator, suppressed the release of gonadotropins induced by either I-GnRH-III or LHRH, indicating that calcium is required for the action of either peptide. Previous results showed that sodium nitroprusside, a releaser of nitric oxide (NO), causes the release of both FSH and LH from hemipituitaries incubated in vitro. In the present experiments, a competitive inhibitor of NO synthase, L-NG-monomethyl-Larginine (300 μM) blocked the action of I-GnRH-III or partially purified FSHRF. The results indicate that I-GnRH-III and FSHRF act on putative FSHRF receptors by a calcium-dependent NO pathway.
KW - FSHRF receptors
KW - NO synthase
KW - cGMP
KW - m-LHRH receptors
UR - http://www.scopus.com/inward/record.url?scp=0036791489&partnerID=8YFLogxK
U2 - 10.1177/153537020222700910
DO - 10.1177/153537020222700910
M3 - Article
C2 - 12324658
AN - SCOPUS:0036791489
SN - 0037-9727
VL - 227
SP - 786
EP - 793
JO - Experimental Biology and Medicine
JF - Experimental Biology and Medicine
IS - 9
ER -