Fig. 1. Dose-responses of various melanocyte cultures to 
-MSH. The responses
of NHM 753-c, 830-c, 849-b and 755-c, homozygous or compound heterozygous for
MC1R variants, and NHM 747-c, 729-c and 751-b, homozygous for the
consensus MC1R were compared. The response of NHM 765-c, heterozygous
for Val92Met substitution, is also presented, since it is comparable to NHM
753-c and 830-c in the ratio of eumelanin to pheomelanin. The responses to
-MSH were tested as described in the Materials and Methods. The effects
of increasing doses of -MSH on cAMP formation, tyrosinase activity and
cell proliferation are presented in A, B and C, respectively. Basal levels of
cAMP (Pmole/106 cells) in the cultures tested were as follows:
753-c=2.176±0.134; 830-c=1.451; 849-b=1.172±0.0219;
755-c=2.193±0.206; 765-c=1.675±0.137; 747-c=1.074±0.098;
729-b=2.007±0.128; 751-b=0.84±0.103. In A and B, each value
represents the mean percent of control of six determinations±s.e. In C,
each value is the mean percent of control of three
determinations±s.e.
