Changes in Pituitary LH Content During the Rat Estrous Cycle1

Luteinizing Hormone Concentrations in Pituitary and in Blood Plasma During the Estrous Cycle of the Rat

“…triggers somehow the neuro-humoral mechanism of LH-release from the pituitary. This concept is supported by the finding of Schwartz (1964) who investi- LH and of estrogen, progesterone and 20a-hydroxypregn-4-en-3-one(20a-OHP) in ovarian venous blood in the rat. The patterns of ovarian steroids are cited from Hori et al(1968) and Uchida et al (1968). gated acute effects of ovariectomy on pituitary LH, uterine weight, and vaginal cornification in the cyclic rats and claimed that the ovary must be in situ on the day before proestrus for the increase in uterine weight and the discharge of pituitary LH to occur.…”

Anterior Pituitary Ovulating Capacity in the PMSG-Primed Immature Female Rat

“…The data from the PMSG-primed females compare favourably with the pituitary lh information on the adult cycling rat (Mills & Schwartz, 1961;Schwartz & Bartosik, 1962) where pituitary lh decreased during the critical period, but lowest lh values were seen on the morning of oestrus. However, no pituitary change was seen between 14.00 and 19.00 hours in PMSG-ovulated 27-day-old females, but a significant fsh decrease occurred (Rennels & O'Steen, 1967 (Ramirez & Sawyer, 1965a) have shown an increase in the lh-rf in prooestrus, continuing for some time after the critical period, and followed by a decrease which is maintained into the morning of oestrus.…”

“…Progesterone administration on the day before pro-oestrus in 5-day cycling adult female rats causes ovulating hormone release 24 hr earlier than normal (Everett & Sawyer, 1949b (Ramirez & McCann, 1964;Schwartz & Calderelli, 1965). Phénobarbital blocked the lh increase in the afternoon of pro-oestrus (Schwartz & Calderelli, 1965 (Cole, 1936;Strauss & Meyer, 1962 (Mills & Schwartz, 1961;Schwartz & Bartosik, 1962;Rennels & O'Steen, 1967) have been shown to decrease during the critical period and both exogenous lh and fsh can cause ovulation (Zarrow, Caldwell, Hafez & Pincus, 1958;Zarrow & Gallo, 1966 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 0/9 9/9 9/9 9/9 9/9Î 9/9t 9/9Î 9/9Î 0/9 0/9 0/9 0/9 0/9 9/9 9/9 9/9 9/9Í 0/12 11/11 12/12 9/9 10/llt 10/llt 13/13Î 12/12J (5/9)t (6/8) (4/9) (4/9) (4/9) (4/9) (7/9) (3/9) (4/9) (3/9) (0/9) (0/9) (0/9) (0/9) (0/9) (0/9) (0/9) (0/9) (7/9) (4/9) (3/9) (3/8) (1/9) (0/9) (0/9) (0/9) (0/9) (3/12) (1/ ) (1/12) (1/9) (1/11) (1/11) (0 (7/9) (9/9) (9/9) (9/9) (8/9) (8/9) (8/9) (8/9) (9/9) (8/9) (6/9) (0/9) (1/9) (1/9) (2/9) (4/9) (1/9) (3/9) (9/9) (9/9) (7/9) (9/9) (2/9) (0/9) (1/9) (0/9) (1/9) (8/12) (4/11) (7/12) (8/9) (7/11) (10/11) (6/13) (7 (Bogdanove, 1964). Therefore, in the 16.30 PB rat oh synthesis occurs.…”

Effect of Electrical Stimulation of the Brain on Ovulation during Estrous Cycle in the Rats

“…LH content in the pituitary gland during estrous cycle was reported by Schwartz and Bartosik (1962), Anderson and McShan (1966), Kobayashi et al (1968) and Monroe et al, (1969). Although their results conflicted in some ways, LH content in the pituitary gland on the day of estrus through diestrus II was one half to one third of that Brown-Grant (1969) observed that estrogen facilitated ovulation one day in the 4-day cyclic rat treated by estrogen on the day of diestrus I and by progesterone on the day of diestrus II.…”

“…The LH content in the pituitary is already high during the morning of proestrus before the critical period (Schwartz and Bartosik, 1962;Anderson and McShan 1966;Kobayashi et al, 1968;Monroe et al, 1969), but it is not released until afternoon, although Zeilmaker (1966), Nallar et al (1966), Redmond (1968) and Brown-Grant (1967) showed an enhancement of LH release by progesterone several hours before the critical period. Progesterone delays the critical period, eventually ovulation, if it is given about 20 hr before, on the afternoon of diestrus II (Zeilmaker 1966;Caligaris et al, 1968).…”