No juvenile arterial hypertension in sheep multiples despite reduced nephron numbers.

Low birth weight is associated with an increased risk of metabolic dysfunction and arterial hypertension in later life. Because of their reduced birth weight twins have been used repeatedly as a natural model to investigate prenatal programming of hypertension. To reveal an early impact of lower nephron endowment on blood pressure, we performed a longitudinal study on lambs from single, twin and triplet pregnancies. The lambs were studied from birth until adulthood, including regular blood analyses, measurements of body weight and blood pressure and post-mortem estimation of glomerular numbers. Relative weight differences between multiples and singletons at birth were -28% for twins and -44% for triplets, respectively. Some lambs showed rapid catch-up growth. Total nephron number of twins and triplets was reduced by 21 and 37% with respect to that of singletons (p < 0.01). However, multiples did not show increased blood pressure within the time frame of this study. No gender-specific effect was observed. Plasma concentrations of creatinine, urea, electrolytes or osmolality also did not differ. Our data indicate that the previously reported postnatal blood pressure differences between sheep multiples and singletons are a time-limited phenomenon. During infancy and adolescence, a reduced nephron number in sheep multiples is neither associated with increased blood pressure nor reflected by plasma parameters.

Lanthanides potentiate TRPC5 currents by an action at extracellular sites close to the pore mouth.

Mammalian members of the classical transient receptor potential channel (TRPC) subfamily (TRPC1-7) are Ca(2+)-permeable cation channels involved in receptor-mediated increases in intracellular Ca(2+). Unlike most other TRP-related channels, which are inhibited by La(3+) and Gd(3+), currents through TRPC4 and TRPC5 are potentiated by La(3+). Because these differential effects of lanthanides on TRPC subtypes may be useful for clarifying the role of different TRPCs in native tissues, we characterized the potentiating effect in detail and localized the molecular determinants of potentiation by mutagenesis. Whole cell currents through TRPC5 were reversibly potentiated by micromolar concentrations of La(3+) or Gd(3+), whereas millimolar concentrations were inhibitory. By comparison, TRPC6 was blocked to a similar extent by La(3+) or Gd(3+) at micromolar concentrations and showed no potentiation. Dual effects of lanthanides on TRPC5 were also observed in outside-out patches. Even at micromolar concentrations, the single channel conductance was reduced by La(3+), but reduction in conductance was accompanied by a dramatic increase in channel open probability, leading to larger integral currents. Neutralization of the negatively charged amino acids Glu(543) and Glu(595)/Glu(598), situated close to the extracellular mouth of the channel pore, resulted in a loss of potentiation, and, for Glu(595)/Glu(598) in a modification of channel inhibition. We conclude that in the micromolar range, the lanthanide ions La(3+) and Gd(3+) have opposite effects on whole cell currents through TRPC5 and TRPC6 channels. The potentiation of TRPC4 and TRPC5 by micromolar La(3+) at extracellular sites close to the pore mouth is a promising tool for identifying the involvement of these isoforms in receptor-operated cation conductances of native cells.