Hypertension in cafeteria-fed rats:: Alterations in renal α2-adrenoceptor subtypes

Obesity is a major cause of human essential hypertension and there are clear evidences that abnormal kidney functions play a key role in obesity hypertension. Feeding rats a cafeteria diet has been extensively used as an experimental model to study obesity and energy balance expenditure. The present study investigated whether rats fed a cafeteria diet develop hypertension with alterations in renal cr,adrenoceptor subtype distribution. Weight gain induced by feeding rats a cafeteria diet during 8 weeks was associated with a marked increase in blood pressure. Insulin levels were higher in these hypertensive rats, leading to a decreased plasma glucose/insulin ratio. Based on radioligand-binding studies using [H-3]-RX821002 and selective competitors, a raise in alpha(2)-adrenoceptor density that was solely due to an increased alpha(2)beta-adrenoceptor subtype density was detected in the kidney of the cafeteria-fed rat. Furthermore, reverse transcription-polymerase chain reaction (RT-PCR) experiments showed an overexpression of the gene encoding the rr,B-adrenoceptor subtype in these rats. On the other hand, despite a similar mRNA level, the alpha(2)A-adrenoceptor subtype was no more detectable by radioligand-binding studies in the kidney of the cafeteria-fed rat. In conclusion, cafeteria-fed rats are hypertensive, with renal alterations in cu,adrenoceptor distribution. These alterations, which are not related to genetic factors, may play a key role in the onset of hypertension. (C) 2000 American Journal of Hypertension, Ltd.