Comparison of l-serine uptake by human placental microvillous membrane vesicles and placental villous fragments

Comparison of ¹⁴C-l-serine uptake into placental villous fragments and MVM vesicles prepared from the same placentas. The MVM vesicle uptakes were conducted using our standard protocol (n = 6) and with an adapted protocol (n = 5) where the tracer concentration was reduced from 7.5 to 3 μM as used the fragment studies and of Na⁺ independent uptake was measured in the presence of choline chloride, rather than KCl, as in the fragment studies. There are significant differences in the proportion of uptake by different components, primarily due to a difference in the Na⁺-dependent uptake which was not mediated by system A. Significant differences between the MVM vesicles and villous fragments are indicated by *P < 0.05 vs villous fragments, ^ϕP < 0.001 vs fragments. Data is mean ± SEM.

Relative serine uptake by different transport components in placental villous fragments and MVM vesicles measured in the same placentas. While the relative activity of system A and system L were not significantly different there were differences between the techniques in relation to Na⁺ dependent/Na⁺ independent activity and system A/Na⁺ dependent activity. This indicates that while there are differences between the methodologies for some transport components others, such as system A and system L, are comparable. *P < 0.05 vs villous fragments, ^ϕP < 0.001 vs villous fragments. Data is mean ± SEM, n = 5 or 6.