Pulsatile growth hormone secretion, circulating insulin-like growth factor-1 concentration and cellular density of somatotrophs differ between Wagyu and Holstein steers

Abstract

Japanese Black cattle (Wagyu), deposit much higher amounts of intramuscular fat, known as marbling, than other breeds of cattle. To determine whether this unique fat deposition is attributable to the somatotropic axis, we compared pulsatile growth hormone (GH) secretion, plasma levels of insulin-like growth factor-1 (IGF-1) and cellular density of somatotrophs (GH-expressing cells) in the anterior pituitary glands of Japanese Black and Holstein steers. Blood samples were withdrawn every 15 min for 6 h from 14 Japanese Black and 12 Holstein steers at about 17 months of age, and GH and IGF-1 concentrations were determined. The distribution and proportion of GH-expressing cells were analysed by immunohistochemistry combined with point-count morphometry in pituitaries from six steers from each breed aged about 18 to 21 months. Overall mean and baseline plasma GH concentrations were lower (P < 0·001) in Japanese Black than Holstein steers. In addition, Japanese Black had smaller (P < 0·05) amplitudes of GH secretory pulses than Holstein steers, whereas the GH pulse frequency did not differ between the breeds. Japanese Black steers also had lower (P < 0·001) plasma levels of IGF-1 than Holstein steers. The marbling score of Japanese Black steers was higher (P < 0·001) than that of Holsteins at the same carcass weight. The proportion of GH-expressing cells was smaller (P < 0·05) in Japanese Black than Holstein steers at the hind dorsal and hind ventral regions of the adenohypophysis. Thus, in Japanese Black and Holstein steers, the breed difference in the relative density of GH-expressing cells corresponded to that in profiles of pulsatile GH secretion. These results suggest that the features of the somatotropic axis intrinsically differ between Japanese Black and Holstein cattle and that these features may be partly responsible for the genetic ability of the former to deposit greater amounts of marbling fat and for the smaller frame of Wagyu cattle.

Immunohistochemical detection of pituitary transcription factor‐1 in paraffin sections of bovine adenohypophysis after wet heat‐induced antigen retrieval

“…The proportion of GH cells per Pit‐1 immunoreactive cells was smaller in the adenohypophysis of Blk than Hol steers although there was no difference in the cellular density of Pit‐1 immunoreactive cells between the two breeds. This suggests that cellular composition of GH, PRL and TSH cells is different between Blk and Hol cattle, and conforms with our previous result (Matsuzaki et al . 2001) reporting that the frequency of GH cells in the Blk is intrinsically less than that in Hol cattle.…”

“…The adenohypophysis of Japanese Black (Blk) steers is less densely populated with somatotrophs (GH cells) than that of Holstein (Hol) steers, and the difference corresponds well with the different activity of pulsatile GH secretion observed between the breeds (Matsuzaki et al . 2001).…”

“…The protocol used in the present study conformed to local regulations concerning the health and care of experimental animals. Animals and their husbandry have been described previously (Matsuzaki et al . 2001).…”

Endocrine Characteristics of Cloned Calves

“…The intra-and interassay CV were 6.7% and 13.3%, respectively. Plasma samples for the analysis of IGF-I were extracted using the acid-ethanol cryoprecipitation method (Breier et al, 1991) and analyzed by the similar RIA procedure described previously (Matsuzaki et al, 2001). Recombinant human (rh) IGF-I (CU 100, GroPep Pty Ltd.) was used as the radioligand and standard.…”

Characteristics of milk production and plasma levels of growth hormone and insulin in Japanese Black cows

“…In addition to the hormonal profi les, the proportion of GH-expressing cells at the adenohypophysis is smaller in Japanese Black than in Holstein steers (Matsuzaki et al, 2001). Thus, based on the hormonal and morphological profi les during the growing stage, there may be a difference in the secretion of GH and insulin between beef and dairy cows during lactation.…”