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Possible discrimination between genotypes of lactase persistence phenotype

B. Beiguelman^I; A. Sevá-Pereira^I; A.C. Sparvoli^II

^IFaculdade de Ciências Médícas, UNICAMP, Caixa Postal 6111, 13081 Campinas, SP, Brasil. Send correspondence to B.B.
^IIFaculdade de Medicina, Fundação Universidade Federal do Rio Grande, 96200 Rio Grande, RS, Brasil

ABSTRACT

Persistence of lactase activity in adult life is accepted to be inherited as an autosomal dominant trait. However, investigation of the frequency of adult-type hypolactasia among Brazilian Caucasoids suggests that homozygous lactose absorbers may be distinguished from heterozygous absorbers. A lactose loading test was applied to 88 healthy adult volunteers, glucose levels being determined in venous blood samples collected before, 20, 40 and 60 minutes after this test. The distribution of the maximum blood glucose rise (MBGR) of the examined individuals, instead of the expected bimodal distribution, suggested trimodality, corresponding to three phenotypes: adult-type hypolactasia (MBGR less than 16 mg%), heterozygous lactose absorbers (MBGR between 16 and 56 mg%) and homozygous lactose absorbers (MBGR of 56 mg% or higher). The observed distribution agrees well with that expected according to the Hardy-Weinberg law.

Keywords: Lactase.

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