Concentrations and pulse analyses of adrenocorticotrophin and luteinizing hormone in plasma from dogs in pro-oestrus, oestrus, dioestrus or anoestrus.

Concentrations of adrenocorticotrophin (ACTH) and luteinizing hormone (LH) were measured in plasma collected every 5 min for 190 min from bitches during the oestrous cycle to determine whether mean concentration of ACTH in plasma changes with oestrous cycle phase, and to determine whether plasma ACTH peaks, if present, are related to LH peaks. Radioimmunoassays (RIA) validated for use with dog plasma were used. Mean concentration of ACTH in plasma from pro-oestrous dogs [12.7 +/- 6.0 (SD) range: 5.7-23.1 pmol l-1] was slightly higher (P = 0.085) than that in dogs in oestrus (7.9 +/- 2.1, range: 5.0-11.9 pmol l-1), dioestrus (7.8 +/- 1.5, range: 6.0-9.8 pmol l-1), or anoestrus (7.5 +/- 1.5, range: 5.2-9.2 pmol l-1). Mean concentration of LH in plasma from pro-oestrous dogs [6.0 +/- 7.6 (SD), range: 1.0-19.1 ng ml-1] was higher (P < 0.05) than that in dogs in oestrus (0.6 +/- 0.8, range: undetectable to 2.2 ng ml-1), dioestrus (1.6 +/- 2.1, range: 0.7-5.9 ng ml-1), or anoestrus (1.4 +/- 1.3, range 0.1-3.4 ng ml-1). Plasma ACTH and LH peaks were detected in some dogs during each phase of the cycle. Mean frequency of ACTH peaks (range 0-3 peaks) was similar in all oestrous cycle phases. When data from all phases were combined, mean (+/- SD) number of ACTH peaks in 190 min, interpeak interval and peak duration were 1.7 +/- 1.1, 50 +/- 21, and 34 +/- 7.7 min, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)