beta-fibrinogen allele frequencies in Peruvian Quechua, a high-altitude native population

Elevated hematocrits, which are found in many high-altitude populations, in crease the oxygen-carrying capacity of blood and may represent an adaptatio n to hypoxic environments. However, as high hematocrit increases blood visc osity, which in turn is associated with hypertension and heart disease, it may be advantageous for high-altitude populations to limit other factors th at contribute to increased blood viscosity. One such factor is the plasma c oncentration of the coagulation protein fibrinogen. Several common polymorp hisms in the P-fibrinogen gene have been identified that affect fibrinogen concentrations. We determined the allele frequencies of three of these poly morphisms (G/A(-455)(HaeIII), C/T-148(HindIII), and G/A(+448)(MnlI)) in sam ple groups drawn from three populations: Quechua-speaking natives living at over 3,200 m in the Peruvian Andes, North American natives (Na-Dene) from coastal British Columbia, and Caucasian North Americans. The frequencies of the alleles previously shown to be associated with increased fibrinogen le vels were so low in the Quechuas that their presence could be accounted for solely by genetic admixture with Caucasians. Frequencies in the Na-Dene, a Native American group unrelated to the Quechua, were not significantly dif ferent from those in Caucasians. (C) 1999 Wiley-Liss, Inc.