Expression of beta 1- and beta 2-receptor genes and correlation to lipolysis in human adipose tissue during childhood.

beta 1- and beta 2-adrenoceptor (bar1 and bar2) mRNA levels were measured in adipose tissue obtained from children (between 1 month and 10 yr of age) and adults during inguinal hernia operations. Bar1 mRNA levels were constant in all age groups studied. In infants and children less than 7 yr old, bar2 levels were twice as high (P < 0.01) as those in adults, and in infants 1-4 months old, bar2 mRNA levels were higher than bar1 levels (P < 0.01). The bar2/bar1 ratio gradually decreased, and in adults, there was 2.3-fold higher bar1 mRNA expression (P < 0.01). In infants 1-5 months old, the lipolytic sensitivity to noradrenaline was 5 times lower (P < 0.05) than that in adults, whereas the sensitivity to adrenaline and isoprenaline was unchanged. The maximal lipolytic response to adrenaline was higher than that to noradrenaline in infants (P < 0.01), whereas the opposite was found in adults (P < 0.01). The lipolytic sensitivity to the bar1-selective agonist dobutamine was not influenced by age, whereas the sensitivity to the bar2-selective agonist terbutaline was 10,000 times higher in infants than in adults. In conclusion, these data indicate subtype-specific developmental changes in bar expression, with higher bar2 mRNA levels accompanied by increased bar2-induced lipolysis during infancy.