Evaluating Functional Status Of HPGA In Young Female Rats By Gonadotropin Concentrations In Urine After Injected Gonadotropin-releasing Hormone

Objective To evaluate functional status of hypothalamic-pituitary-gonadal axis (HPGA) of young female rats, tracking gonadotropin (Gn) concentrations in urine by immunochemiluminometric assay(ICMA) in order to explore a convenient, reliable and intact Gonadotropin-releasing hormone(GnRH) stimulating test。Methods Sixty young female rats (postnatal 21 days) were randomized into four groups equally: experiment group, control group 1, control group 2 and control group 3. On postnatal 38 days, experiment group i.m. triptorelin to suppress HPGA, but control group 1 and control group 2 i.m. 0.9%NaCl; During three periods of postnatal 25²7 days(no vaginal opening), postnatal 35³7 days(all vaginal opening) and postnatal 72⁷4 days, injected with either 7.5ug/kg GnRH (experiment group and control group 1) or 0.9%NaCl (control group 2) ,8-h urinary Luteinizing hormone(LH)and Follicle-stimulating hormone (FSH) measured by ICMA were performed before as well as after injection, adjusted by Creatin(Cr). vaginal smear was observed. On postnatal 75 d, experiment group, control group 1 and control group 2 were decapitated. Ovaries, uteri and vagina were rapidly removed for histopathology. On postnatal 25 days control group 3 decapitated and ovaries were observed by histopathology.Result (1)On postnatal 25²7 days, LH/Cr in urine(IU/mol)of experiment group, group control 1 and group control 2 before injected GnRH or 0.9%NaCl were 279.61±44.86, 267.62±54.15 and 274.82±53.45, respectively; FSH/Cr in urine (IU/mol)were 90.11±23.75,87.22±12.63 and 88.64±23.12, respectively . LH/Cr in urine(IU/mol)after injected GnRH or 0.9%NaCl were 286.07±44.97,272.61±52.81 and 269.82±38.62, respectively;FSH/Cr in urine(IU/mol)were 88.67±20.94,86.54±13.06 and 89.47±23.15, respectively. LH/Cr and FSH/Cr in urine were no significant differences among the three groups before injected GnRH or among the three groups after injected GnRH, or comparing after injection to before. (2) On postnatal 35³7 days, LH/Cr in urine(IU/mol)of experiment group, group control 1 and group control 2 before injected GnRH or 0.9%NaCl were 294.17±27.67,283.05±20.33 and 292.73±32.72, respectively; FSH/Cr in urine (IU/mol)were 91.22±29.29, 86.76±23.34 and 86.99±15.20, respectively . LH/Cr in urine(IU/mol) after injected GnRH or 0.9%NaCl were 607.52±54.73,586.56±53.30 and 280.18±50.22, respectively; FSH/Cr in urine(IU/mol)were 141.13±57.64,133.54±32.51 and 88.20±19.13,respectively. Before injected GnRH, LH/Cr and FSH/Cr in urine were no significant differences among the three groups; After injected GnRH,LH/Cr and FSH/Cr in urine of experiment group and group control 1 were significantly higher compared to group control 2.(F_LH/Cr =172.162,PLH/Cr<0.01; HFSH/Cr=12.345,PFSH/Cr<0.01); LH/Cr in urine of experiment group and group control 1 was significantly higher after injected GnRH compared to before injected(t_{experiment group} =-21.427,P_{experiment group} <0.01; t_{group control 1} =-20.659,P_{group control 1}<0.01),as well as FSH/Cr in urine(t_{experiment group} =-3.741,P_{experiment group} <0.01; t_{group control 1}=-4.412,P_{group control 1}<0.01),LH/Cr and FSH/Cr in urine of group control 2 were no significant differences comparing after to before injection.(3) On postnatal 72⁷5 days, LH/Cr in urine(IU/mol)of experiment group, group control 1 and group control 2 before injected GnRH or 0.9%NaCl were 128.88±23.50,280.12±22.46 and 272.38±30.22, respectively;FSH/Cr in urine (IU/mol) were 49.44±18.05,87.56±14.61 and 86.24±16.69,respectively . LH/Cr in urine (IU/mol) after injected GnRH or 0.9%NaCl were 126.69±27.92,597.89±36.47 and 272.42±30.34, respectively;FSH/Cr in urine(IU/mol)were 42.15±13.75,120.35±16.85 and 95.04±15.76,respectively. Before injected GnRH, LH/Cr and FSH/Cr in urine of experiment group were significantly lower compared to group control 1 and group control 2(F_LH/Cr=165.692,PLH/Cr<0.01; FFSH/Cr=25.523,PFSH/Cr<0.01); After injected GnRH,LH/Cr and FSH/Cr in urine of group control 1 were significantly higher compared to experiment group and group control 2(F_LH/Cr=860.614,PLH/Cr<0.01; FFSH/Cr=99.241,PFSH/Cr<0.01); LH/Cr and FSH/Cr in urine of group control 1 were significantly higher after injected GnRH compared to before injected(tLH/Cr=-29.734,PLH/Cr<0.01;tFSH/Cr=-6.357,PFSH/Cr<0.01),but LH/Cr and FSH/Cr in urine of experiment group and group control 2 were no significant differences comparing after injection to before. (4)After experiment group and group control 1 injected GnRH, LH/Cr in urine was significantly lower on postnatal 72⁷4 days comparing to postnatal 25～27 days and postnatal 35～37 days (H=74.176, P<0.01), as well as FSH (H =61.657,P<0.01).The sensitivity and specificity of urinary LH determinations (LH/Cr>426.29IU/mol)to detect HPGA activity were 100% and 100%, respectively. For urinary FSH determinations(FSH/Cr>108.96 IU/mol), the sensitivity and specificity were 93.8% and 85.7%, respectively.Conclusion After injected GnRH in young female rats, the sensitivity and specificity of urinary LH determinations(LH/Cr>426.29IU/mol)to detect inadequate HPGA suppression were 100% and 100%, respectively, seemed suitable for evaluating functional status of HPGA.