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α1c- and β2-adrenergic receptor mRNA distribution in the bovine mammary gland detected by competitive RT-PCR

Published online by Cambridge University Press:  16 April 2002

OLGA WELLNITZ
Affiliation:
Institut für Tierzucht, Universität Bern, CH-3012 Bern, Switzerland Present address: Institut für Anatomie, Physiologie und Hygiene der Haustiere, Universität Bonn, D-53115 Bonn,Germany.
ANDREAS ZURBRIGGEN
Affiliation:
Institut für Tierneurologie, Universität Bern, CH-3012 Bern, Switzerland
ROBERT R. FRIIS
Affiliation:
Department für klinische Forschung, Universität Bern, CH-3012 Bern, Switzerland
JÜRG W. BLUM
Affiliation:
Institut für Tierzucht, Universität Bern, CH-3012 Bern, Switzerland
RUPERT M. BRUCKMAIER
Affiliation:
Institut für Tierzucht, Universität Bern, CH-3012 Bern, Switzerland Present address: Institut für Physiologie, Technische Universität München, Weihenstephan, D-85350 Freising,Germany.

Abstract

Milk ejection and milk removal is considerably influenced by the sympathetic nervous system. Stimulation of α-adrenergic receptors by administration of α-adrenergic agonists inhibits alveolar milk ejection and milk removal in dairy cows due to smooth muscle contraction (Blum et al. 1989; Bruckmaier et al. 1991). However, contraction of the teat in response to α-adrenergic receptor stimulation has no influence on milk flow as long as milk is available in the cistern (Bruckmaier et al. 1997). Therefore, α-adrenergic stimulation causes inhibition of transport of alveolar milk into the cistern. On the contrary, the stimulation of β-adrenergic receptors facilitates milk ejection and milk removal in dairy cows (Bernabé & Peeters, 1980; Bruckmaier et al. 1991) because of muscle relaxation. Therefore, the distribution of α- and β-adrenergic receptors plays an important role in the milkability of dairy cows. However, from these in vivo studies it is not possible to distinguish between the different α1- and α2- and β2-receptor subtypes owing to the non-specific nature of the pharmacological agents used.

To date, the precise tissue distribution of these different subtypes, in bovine mammary tissue, is unknown. Using molecular techniques, we were interested in the expression of genes that encode α1c and β2 as a preliminary study towards the understanding of noradrenergic receptor-gene expression and regulation in this important system.

In addition, α1c- and β2-adrenergic receptors were determined in front and rear quarters of the mammary gland to investigate differences in receptor distribution within the udder and possible relations between adrenergic receptor distribution and the higher milk flow rates in rear than in front quarters (Rothenanger et al. 1995).

Type
Brief Report
Copyright
Proprietors of Journal of Dairy Research 2001

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