Organ-specific overexpression of renal LAT2 and enhanced tubular L-DOPA uptake precede the onset of hypertension.
Spontaneously hypertensive rats (SHR) might have increased renal production of dopamine. L-3,4-Dihydroxyphenylalanine (L-DOPA) uptake in renal epithelial cells is promoted through the type 2 L-type amino acid transporter (LAT2), and this might rate-limit the synthesis of renal dopamine. The present study evaluated L-DOPA uptake in isolated renal proximal tubules of SHR and normotensive controls (Wistar-Kyoto rats [WKY]). Expression of LAT1 and LAT2 in the renal cortex and intestinal mucosa was also evaluated. Tubular uptake of L-DOPA in WKY and SHR was a saturable process, being greater in the latter than the former at both 4 and 12 weeks of age. cDNA fragments (LAT1, 688 bp; LAT2, 729 bp) labeled with 32P were used as probes for Northern blot analysis. Expression of LAT2 in SHR kidneys was higher than in WKY kidneys. This increase was more marked at 4 than at 12 weeks of age. Intestinal LAT2 expression, however, was identical in SHR and WKY at both 4 and 12 week of age. By Northern blot analysis, the LAT1 transcript was not identified in either the kidney or intestine. Kidney total RNA was then reverse-transcribed and amplified by polymerase chain reaction with specific primers for LAT1. The presence of a fragment of the expected size for LAT1 led to the conclusion that LAT1 mRNA is a rare message in kidney. We conclude that overexpression of LAT2 in the SHR kidney might contribute to the enhanced L-DOPA uptake, which is organ specific and precedes the onset of hypertension.
Pinho
Maria João
MJ
Institute of Pharmacology and Therapeutics, Faculty of Medicine, Porto, Portugal.
Gomes
Pedro
P
Serrão
Maria Paula
MP
Bonifácio
Maria João
MJ
Soares-da-Silva
Patrício
P
D027182:Amino Acid Transport System y+; D000818:Animals; D001142:Aromatic-L-Amino-Acid Decarboxylases / Q000378:metabolism; D001692:Biological Transport; D027301:Fusion Regulatory Protein 1, Light Chains / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D006973:Hypertension / Q000209:etiology / Q000235:genetics / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D027283:Large Neutral Amino Acid-Transporter 1 / Q000235:genetics / Q000378:metabolism; D007980:Levodopa / Q000378:metabolism*; D008297:Male; D009928:Organ Specificity; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
D027182:Amino Acid Transport System y+; D027301:Fusion Regulatory Protein 1, Light Chains; D027283:Large Neutral Amino Acid-Transporter 1; D012333:RNA, Messenger; C486582:Slc7a8 protein, rat; D007980:Levodopa; D001142:Aromatic-L-Amino-Acid Decarboxylases