Differential role of adrenoceptors in control of plasma glucose and fatty acids in carp, Cyprinus carpio (L.).
Carp were cannulated in the dorsal aorta, and after 2 days of recovery they were infused with 1) norepinephrine, 2) yohimbine (alpha(2)-antagonist) plus norepinephrine, 3) clonidine (alpha(2)-agonist), and 4) isoproterenol (nonselective beta-agonist). Norepinephrine lowered the plasma free fatty acid (FFA) level and raised the plasma glucose level for several hours. Norepinephrine in combination with the alpha(2)-antagonist yohimbine resulted in retardation of the FFA decrease, indicating the involvement of alpha(2)-adrenoceptors. Infusion with the partial alpha(2)-agonist clonidine had a smaller effect. Infusion with isoproterenol caused a marked increase of glucose levels, and unexpectedly a decline of plasma FFA levels, indicating a direct involvement of beta-adrenoceptors. Combination of isoproterenol with either atenolol (beta(1)-antagonist) or ICI-118,551 (beta(2)-antagonist) showed that both beta(1)- and beta(2)-adrenoceptors were involved in the glucose release by isoproterenol. Remarkably, the decline of FFA levels was augmented in the presence of ICI-118,551, whereas with atenolol present plasma FFA levels were increased by isoproterenol. Thus it is concluded that in carp both beta(1)- and beta(2)-adrenoceptors mediate glucose release, whereas lipolysis is controlled by inhibitory beta(1)-adrenoceptors and stimulatory beta(2)-adrenoceptors, as well as by inhibitory alpha(2)-adrenoceptors.
van den Thillart
G
G
Institute of Evolutionary and Ecological Sciences, Van der Klaauw Laboratories, 2300 RA Leiden, The Netherlands. thillart@rulsfb.leidenuniv.nl
Vianen
G
G
Ponce
M C
MC
Lelieveld
H
H
Nieveen
M
M
Van Raaij
M
M
Steffens
A
A
Zaagsma
J
J
D000322:Adrenergic Agonists / Q000097:blood; D000316:Adrenergic alpha-Agonists / Q000097:blood; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D001786:Blood Glucose / Q000378:metabolism*; D002347:Carps / Q000097:blood*; D003000:Clonidine / Q000494:pharmacology; D004837:Epinephrine / Q000097:blood*; D005230:Fatty Acids, Nonesterified / Q000097:blood*; D007545:Isoproterenol / Q000494:pharmacology; D019344:Lactic Acid / Q000097:blood; D009638:Norepinephrine / Q000494:pharmacology*; D011412:Propanolamines / Q000494:pharmacology; D011943:Receptors, Adrenergic, beta / Q000502:physiology*; D015016:Yohimbine / Q000494:pharmacology
D000322:Adrenergic Agonists; D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D000318:Adrenergic beta-Agonists; D000319:Adrenergic beta-Antagonists; D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D011412:Propanolamines; D011943:Receptors, Adrenergic, beta; D015016:Yohimbine; D019344:Lactic Acid; C026777:ICI 118551; D001262:Atenolol; D007545:Isoproterenol; D003000:Clonidine; D009638:Norepinephrine; D004837:Epinephrine