Adrenoceptor heterogeneity in human white adipocytes differentiated in culture as assessed by cytosolic free calcium measurements.
Changes in intracellular calcium concentration [Ca2+]i in response to norepinephrine (NE) and to various adrenergic agonists were monitored by dual excitation microfluorimetry in single human adipocytes differentiated in culture and loaded with fura-2 acetoxymethyl ester (fura-2 AM). The addition of NE elicited increases in [Ca2+]i that were depending on the cell, (1) either rapid (time to peak: 9 +/- 3 s), large, and transient; or (2) slow (time to peak: 125 +/- 8 s), small, and sustained. The rapid and large [Ca+]i response, which was inhibited by 90% by the alpha 1-antagonist prazosin and only by 20% by the non-specific beta antagonist (-)-propranolol, was considered to be mediated by the alpha 1-adrenoceptor. In fact, an alpha 1A-adrenoceptor was found to be expressed in human white adipose tissue. Consecutive additions of beta-agonists specific for each subtype of alpha-adrenoceptor enabled the characterization of four cell populations with different response patterns: 47% of the cells had alpha 1- and beta 1-, beta 2- and beta 3-induced [Ca2+]i responses; 29% had only beta 1-, beta 2-, beta 3-responses; 14% had alpha 1- and beta 3-responses, and 10% had only an alpha 1-response. Taken together, these results show that in differentiated human adipocytes: (1) alpha 1- and beta-adrenergic stimulations induce [Ca2+]i increases with different kinetics and amplitudes; (2) there is a beta 3-adrenergic response similar to the beta 1- or beta 2-adrenergic responses; and (3) there is a marked adrenoceptor heterogeneity.
Seydoux
J
J
Départment de Physiologie, Centre Médical Universitaire, Genève, Switzerland.
Muzzin
P
P
Moinat
M
M
Pralong
W
W
Girardier
L
L
Giacobino
J P
JP
D017667:Adipocytes / Q000737:chemistry / Q000166:cytology / Q000502:physiology*; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D001483:Base Sequence; D002118:Calcium / Q000032:analysis*; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured / Q000737:chemistry / Q000166:cytology / Q000502:physiology; D003600:Cytosol / Q000737:chemistry; D016257:Fura-2; D018740:Genetic Heterogeneity; D006801:Humans; D008969:Molecular Sequence Data; D009638:Norepinephrine / Q000494:pharmacology; D009852:Omentum / Q000473:pathology; D011942:Receptors, Adrenergic, alpha / Q000235:genetics*; D011943:Receptors, Adrenergic, beta / Q000235:genetics*
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D011942:Receptors, Adrenergic, alpha; D011943:Receptors, Adrenergic, beta; D002118:Calcium; D016257:Fura-2; D009638:Norepinephrine