LIPOPROTEIN[A] IN THE CHIMPANZEE - RELATIONSHIP OF APO[A] PHENOTYPE TO ELEVATED PLASMA LP[A] LEVELS

Several studies have documented the presence of Lp[a] in nonhuman prim ates. However, data are lacking in great apes such as the chimpanzee. We have studied the quantitative distribution of Lp[a], as well as the frequency of apo[a] phenotypes, in a population of chimpanzees living in Gabon. Monoclonal antibody 14A12, directed against human apo[a], f ailed to recognize chimpanzee Lp[a]. Therefore, Lp[a] was assayed usin g an ELISA involving two polyclonal antibodies, an anti-human apo[a] a nd an anti-human apoB-100. Under these conditions, Lp[a] was detected in each of 28 animals. The plasma level of Lp[a] was found to be highl y skewed toward elevated values: the mean Lp[a] level was 0.61 mg/ml ( SD 0.45) as compared to 0.18 mg/ml (SD 0.16) in a normal Caucasian pop ulation (P < 0.0001). Phenotypes for apo[a] were identified by SDS-aga rose-gel electrophoresis, followed by immunoblotting and detection by chemiluminescence. Seventeen different isoforms (ranging from 440 to 9 20 kDa) were found among all the animals as compared to 19 (540 to 960 kDa) in a human population of equivalent number. However, the distrib ution of apo[a] phenotypes was distinct between these populations. Thu s isoforms of low molecular mass occurred with greater frequency in ch impanzee as compared to humans. In both populations, a strong inverse correlation between Lp[a] levels and apo[a] isoform sizes was found in chimpanzees (r = -0.48; P < 0.01) and in man (r = -0.68; P < 0.0002). Clearly then, chimpanzees differ not only from humans, but also from other nonhuman primates, such as the cynomolgus monkey and baboon, in both the distribution of their Lp[a] levels and the frequency of apo[a ] isoforms.