Plasma gonadotrophins and oestradiol during oestrus in the cow

Abstract

Summary. LH values between \ m=-\ 2 and +4 h (0 h =LH peak) were higher than baseline.FSH values were also raised at this time and between + 16 and + 30h. Oestradiol values between \m=-\20 and 0 h were higher than during + 4 to + 20h.Plasma FSH levels during the bovine oestrous cycle have been measured (Akbar, Reichert, Dunn, Kaltenbach & Niswender, 1974; Deri vaux, Ectors, Hendrick & Franchimont, 1974;Schams & Schallenberger, 1976), but details of the changes in plasma oestradiol concentration and those of LH and FSH during the oestrous period have not been reported. The following investigation was under¬ taken to define the temporal relationship between these hormones. Progesterone concentrations are known to remain basal (<0-5 ng/ml) throughout oestrus (Dobson, Cooper & Furr, 1975). Materials and MethodsSix Friesian heifers, 18-36 months old, were bled (20ml) from indwelling jugular vein catheters every 2 h for 3 days, starting 1 day before oestrus. Plasma was obtained immediately by centrifugation and stored at -15°C. The radioimmunoassays, used without modification, have been described in detail elsewhere. In the LH assay (Dobson et al., 1975) the antibody to bovine LH was raised in a horse by Dr R. B. Snook. The only significant cross-reaction was with TSH (90 %). Purified bovine LH (LER 1072/2) was used as the I25I-labelled preparation. The sensitivity of the method was 0-2 ng with interand intra-assay coefficients of variation of 10-6 and 8-3% respectively. The plasma results are ex¬ pressed as ng equivalents of NIH-LH-B8/ml. For the FSH assay (Dobson, 1978) an antibody to rat FSH (S6 : obtained from NIAMDD) was used. The only significant cross-reaction was 5 % with TSH. Purified bovine FSH (LER-1695-2) was used as the 125I-labelled preparation. The sensitivity of the method was 4 ng with inter-and intra-assay coefficients of variation of 15-5 and 14-5 % respectively. The plasma results are expressed as ng equivalents of NIH-FSH-Bl/ml. The oestradiol assay (Dobson & Dean, 1974) utilized an antibody (R2B2) raised against oestradiol-6-(0-carboxymethyl) oximebovine serum albumin which had no cross-reactions of >2% with any other oestrogen known to occur in the cow. The sensitivity of the method was <10 pg with inter-and intra-assay coefficients of variation of 12-5 and 7-8 %, respectively. ResultsThe changes of LH, FSH and oestradiol concentrations in 6 heifers in relation to the time of maximum LH concentration (0 h) are shown in Text- fig. 1. The mean concentration of oestradiol between -20 and 0 h was significantly higher than during the period 4-20 h after the maximum LH concentration (Student's t test for 2 groups of unpaired data, < 0-001). The LH values between -2 and +4 h inclusive were significantly higher than baseline concentrations (P < 0-001). FSH values between-2 and +4 h were also significantly higher ( < 0-001) than those for periods of 10 h before or after this time. However, FSH values 16-30 h after the LH peak were also significanth/aajged ( < 0-001) compared to the period from 44 to +14 h.

Serum LH concentrations in cyclic buffalo (Bubalus bubalis)

“…Buffaloes 9-13 conceived but Buffalo 14 did not. (1977,1978) and Dobson (1978) (1976) and has also been found in cattle (Snook et al, 1971): it is thought to be correlated with growth and atresia of anovulatory follicles.…”

“…There have been several reports on circulating LH levels during the oestrous cycle in cattle (Bos taurus) (Henricks, Dickey & Niswender, 1970;Snook, Saatman & Hansel, 1971; Madan & Johnson, 1973;Dobson, 1978) and for the zebu (Bos indicus) (Rao, Rao, Rao, Reddy & Rao, 1979). Information on LH concentrations in water buffaloes (Bubalus bubalis), however, is scanty (Heranjal, Sheth, Moodbidri, Desai & Rao, 1976;Sheth, Wadadekar, Moodbidri, Janakiraman & Parameswardan, 1978).…”

Suppression of the secondary FSH surge with bovine follicular fluid is associated with delayed ovarian follicular development in heifers

“…During the bovine oestrous cycle, preovulatory surges of LH and FSH occur simultaneously (Dobson, 1978; and basal plasma concentrations are parallel throughout much of the luteal phase (Rahe et al, 1980;Schallenberger et ai, 1985). However, circulating levels of LH and FSH are clearly divergent during two periods of the oestrous cycle in cattle, suggesting that these times may be critical for ovarian follicular stimulation by appropriate concentrations of each gonadotrophin.…”

“…Following luteolysis, increases in basal LH and *Reprint requests to: Dr J. E. Fortune,823 Veterinary Research Tower, Cornell University, Ithaca, New York 14853, USA. LH pulse frequency (Rahe et al, 1980) are accompanied by decreased FSH concentrations (Butler et ai, 1983;Schallenberger et al, 1984). Patterns of LH and FSH also differ early in the luteal phase, when there is a second increase in plasma FSH but there is no concomitant rise in LH (Dobson, 1978;Roche & Ireland, 1981;. There is evidence that a similar secondary 'surge' in FSH is important for development of follicles for the next ovulatory cycle in rats (Grady et al, 1982).…”

Studies of hormone patterns during the oestrous cycle of beef cows

“…Although further smaller peaks in plasma LH concentrations during the luteal phase have been reported (Schams and Karg, 1969 ;Henricks, Dickey and Niswender, 1970 ;Snook, Saatman and Hansel, 19711, more detailed observations have since shown that, as in other species, episodes of LH secretion occur regularly throughout the cycle and that their frequency and amplitude appear to be dependent on the stage of the cycle (Rahe et al, 1980). A peak in plasma FSH concentrations also occurs at oestrus coinciding with the LH surge (Akbar et al, 1974 ;Schams and Schallenberger, 1976) with a secondary FSH peak of smaller magnitude occurring some 24 h later (Dobson, 1978). Plasma concentrations of oestradiol-170 rise over the four days before oestrus, with a peak occurring on the day before or on the day of oestrus behaviour (Glencross and Pope, 1981 ;Glencross et al, 1981a).…”