The GPCR-Gq/11-PLC system is widely used for cell regulation but the stoichiometry of components in membranes and lipid raft/caveolae microdomains is not known. We thus initiated studies to define such stoichiometry using MDCK-D1 cells. We examined mRNA and protein expression in cell lysates and lysates centrifuged on sucrose density gradients (TritonX-100 and Na2CO3 fractionation). Caveolin (cav)-1-rich fractions were immunoprecipitated (IPed) with cav-1-antisera, probed for co-IPed components and quantitated with recombinant standards on immunoblots. We found similar mRNA abundance for Gαq and Gα11 and observed discordance between mRNA and protein expression. mRNA stoichiometry was: GPCRs (α1b-adrenergic [α1AR] and P2Y2 receptors) > Gαq + Gα11 > PLCβ1 + PLCβ3 while for proteins was: Gαq > PLCβ1 > GPCRs. Initial results reveal different stoichiometry in cav fractions: P2Y2 receptors, Gαq but not Gα11 were enriched in cav fractions and coIPed with cav-1. PLCβ1 did not co-IP with cav-1 but was present in cav fractions. The results thus indicate discordance between mRNA and protein for GPCR-Gq/11-PLC with an absence of “spare receptors” at the protein level. Co-localization of key signaling components in cav-enriched fractions likely contributes to rapid, efficient signaling in the regulation of PLC by GPCR and Gq. (supported by NIH and AHA grants).