303 Clinical Science (1999) 97, 303–312 (Printed in Great Britain) Heterogeneous vascular endothelial growth factor (VEGF) isoform mRNA and receptor mRNA expression in human glomeruli, and the identification of VEGF 148 mRNA, a novel truncated splice variant Catheryne WHITTLE*, Kathleen GILLESPIE*, Rebecca HARRISON†, Peter W. MATHIESON* and Steve J. HARPER* *Academic Renal Unit, University of Bristol, Southmead Hospital, Westbury-on-Trym, Bristol BS10 5NB, U.K., and †Department of Pathology, Southmead Hospital, Westbury-on-Trym, Bristol BS10 5NB, U.K. A B S T R A C T Vascular endothelial growth factor (VEGF) mediates increased vascular permeability and endothelial mitogenesis, and may orchestrate normal glomerular permselectivity and proteinuria. Distinct isoforms result from differential gene splicing. VEGF binds to two cell surface tyrosine-kinase receptors, KDR (kinase domain region) and Flt-1 (fms-like tyrosine kinase-1). The latter also exists in a soluble form (sFlt), which is inhibitory. We have studied patterns of VEGF-isoform and VEGF-receptor expression in isolated single normal human glomeruli. mRNA from 190 glomeruli (from 20 individuals) was harvested on to magnetic beads, and nested reverse transcription–PCR was performed using primers for the VEGF isoforms and VEGF receptors. Simultaneous nested reverse transcription–PCR for CD45 was conducted in order to exclude leucocyte contamination. Unexpected products were isolated, cloned and sequenced. Multiple patterns of glomerular VEGF mRNA isoform expression were identified. Most frequently (58 %), all three common forms were expressed. VEGF 189 (i.e. 189-amino-acid form of VEGF) was expressed in 63 %, VEGF 165 in 85 % and VEGF 121 in 84 % of glomeruli. Two unexpected PCR products were also identified : 18 % of glomeruli expressed VEGF 145 , and 27 % of glomeruli expressed a new truncated VEGF splice variant, VEGF 148 , lacking exon 6, the terminal part of exon 7 and exon 8. Multiple patterns of VEGF-receptor expression were also identified, the most common being expression of all three isoforms (28 %). Overall, KDR was seen in 59 % of glomeruli, Flt-1 in 45 % and sFlt in 57 %. Thus the expression of VEGF within normal glomeruli is complex and variable, with inter- and intra-individual variation. Furthermore, sFlt appears to be the co-dominant form of VEGF receptor expressed within glomeruli, suggesting that, in healthy individuals, a degree of VEGF autoregulation is the norm. The physiological importance of VEGF 148 remains to be confirmed. Key words : glomeruli, permselectivity, proteinuria, VEGF  . Abbreviations : Flt, fms-like tyrosine kinase ; GADPH, glyceraldehyde-3-phosphate dehydrogenase ; KDR, kinase domain region ; RT-PCR, reverse transcription–PCR ; sFlt, soluble form of Flt-1 ; VEGF, vascular endothelial growth factor, Correspondence : Dr S J Harper. The nucleotide sequence data reported have been submitted to the EMBLGenBankDDBJ Nucleotide Sequence Databases under accession no. AFO91352.  1999 The Biochemical Society and the Medical Research Society