title: Role of changes in the pulsatile secretion pattern of FSH in initiation of ovarian folliculogenesis in bitches.
abstract: The results of two studies in which the pulsatile secretion patterns of LH and FSH were investigated in six Beagle bitches during early, mid- and late anoestrus and in six anoestrous Beagle bitches treated with bromocriptine are summarized to improve our knowledge of the endocrine changes that lead to a new follicular phase in bitches. Blood samples for the determination of secretory profiles were obtained via jugular venepuncture at 10 min intervals for 6 h. In untreated bitches, blood samples were collected during early, mid- and late anoestrus. In bromocriptine-treated bitches (20 micrograms kg-1 twice each day, starting 100 days after ovulation until the start of the next oestrous cycle), blood samples were collected before treatment and at 2 week intervals after the start of bromocriptine treatment until the next ovulation. In all bitches, FSH and LH were secreted in a pulsatile manner and FSH pulses coincided with LH pulses. Progression from early to late anoestrus was associated with an increase in FSH secretion without a concomitant increase in LH secretion. The bromocriptine-induced shortening of the interoestrous interval was also associated with an increase in FSH secretion without a concomitant increase in LH secretion. These results indicate that in bitches an increase in circulating FSH should be considered to be a critical event required for the initiation of ovarian folliculogenesis and consequently the termination of anoestrus.
authors.affiliation: Department of Clinical Sciences of Companion Animals, Faculty of Veterinary Medicine, Utrecht University, Yalelaan 8, PO Box 80 154, NL-3508 TD Utrecht, The Netherlands.
authors.forename: H S
authors.initials: HS
authors.lastname: Kooistra
authors.forename: A C
authors.initials: AC
authors.lastname: Okkens
mesh_terms: D000780:Anestrus / Q000502:physiology*; D000818:Animals; D001971:Bromocriptine / Q000494:pharmacology; D004285:Dogs / Q000502:physiology*; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood / Q000378:metabolism*; D006727:Hormone Antagonists / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism; D006080:Ovarian Follicle / Q000187:drug effects / Q000502:physiology*; D012636:Secretory Rate / Q000502:physiology
chemical_list: D006727:Hormone Antagonists; D001971:Bromocriptine; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone