Effects of follicle-stimulating hormone with and without luteinizing hormone on serum hormone concentrations, follicle growth, and intrafollicular estradiol and aromatase activity in gonadotropin-releasing hormone-immunized heifers
Ma. Crowe et al., Effects of follicle-stimulating hormone with and without luteinizing hormone on serum hormone concentrations, follicle growth, and intrafollicular estradiol and aromatase activity in gonadotropin-releasing hormone-immunized heifers, BIOL REPROD, 64(1), 2001, pp. 368-374
To evaluate the roles of FSH and LH in follicular growth, GnRH-immunized an
estrous heifers (n = 17) were randomly assigned (Day 0) to one of three gro
ups (n = 5 or 6). Group 1 received i.m. injections of 1.5 mg porcine FSH (p
FSH) 4 times/day for 2 days; group 2 received i.v. injections of 150 mug pL
H 6 times/day for 6 days; group 3 received both pFSH and pLH as described f
or groups 1 and 2. After slaughter on Day 6, measurements were made of foll
icle number and size, and follicular fluid concentrations of progesterone (
P-4), estradiol (E-2), and aromatase activity. Injection of pFSH increased
(P < 0.01) the serum concentrations of FSH between 12 and 54 h. Infusion of
pLH increased (P < 0.05) mean and basal concentrations of LH and LH pulse
frequency. Serum E-2 concentrations were higher (P < 0.05) for heifers give
n pFSH + pLH than those given either pFSH or pLH alone. There was no differ
ence (P <greater than or equal to> 0.24) between treatments in the number o
f small follicles (<5 mm). Heifers given pFSH or pFSH + pLH had more (P <le
ss than or equal to> 0.02) medium follicles (5.0-9.5 mm) than those that we
re given pLH alone (none present). Heifers given pFSH + pLH had more (P = 0
.04) large follicles (greater than or equal to 10 mm) than those given eith
er pLH or pFSH alone (none present). Overall, only 1 of 35 small follicles
and 2 of 96 medium follicles were E-2-active (i.e., E-2:P-4 >1.0), whereas
18 of 21 large follicles (all in the pFSH + pLH treatment) were E-2-active;
of these, 8 of 18 had aromatase activity. Concentrations of E-2 and E-2 ac
tivity in follicular fluid were correlated (r greater than or equal to 0.57
; P < 0.0001) with aromatase activity in heifers given pLH + pFSH. In concl
usion, pLH failed to stimulate follicle growth greater than 5 mm; pFSH stim
ulated growth of medium follicles that were E-2-inactive at slaughter and f
ailed to increase serum E-2 concentrations; whereas pFSH + pLH stimulated g
rowth of medium follicles and E-2-active large follicles, and a 10- to 14-f
old increase in serum E-2 concentrations.