VASOACTIVE EFFECTS OF BASIC AND ACIDIC FIBROBLAST GROWTH-FACTORS IN HAMSTER-CHEEK POUCH ARTERIOLES

Fibroblasts growth factors (FGFs) exhibit well-known angiogenic action s, but there is some controversy about whether they have vasoactive ef fects on blood vessels which might contribute to angiogenesis per se. To clarify this, changes in arteriolar diameter were recorded during o bservation by videomicroscopy of 3rd- and 4th (terminal)-order arterio les (resting diameters 22.5+/-0.5 mu m and 14.4+/-0.3 mu m, respective ly) in the hamster cheek pouch in response to FGF application. Recombi nant human bFGF (basic) and aFGF (acidic) were applied from micropipet tes positioned 5-10 mu m from the adventitial surface of vessels. Maxi mum vasodilator effects of adenosine (10(-4) M) applied in a similar w ay were also observed. Adenosine increased the diameters of 4th-order arterioles by 37.2+/-3.8% and those of 3rd-order arterioles by 38.7+/- 2.7%. bFGF produced vasodilatation (threshold dose 0.1 ng ml(-1)) in b oth classes of arterioles, while aFGF produced dose-dependent constric tion (threshold dose 0.01 ng ml(-1)). A maximal dilator effect in 4th- order arterioles was obtained with 100 ng ml(-1) bFGF, when diameters reached 82.6+/-2.4% of those with adenosine. Maximal constrictor effec t (-48.2+/-5.6% of resting diameter) occurred with a dose of 100 ng ml (-1) aFGF. Vehicle alone (MOPS or bicarbonate buffer used as solvents for FGFs) had no effect. As vasoconstrictors are known to stimulate gr owth of smooth muscle cells while dilators stimulate growth of endothe lial cells, it is possible that the opposing vasoactivities demonstrat ed for aFGF and bFGF are linked with their selective mitogenicity for smooth muscle and endothelial cells, respectively, and contribute to t heir angiogenic actions.