The kidney is important for eliminating substances from the body and for controlling the amount of fluid in the body, which, in turn, helps regulate blood pressure. One way the kidney senses blood...

The kidney is important for eliminating substances from the body and for controlling the amount of fluid in the body, which, in turn, helps regulate blood pressure. One way the kidney senses blood volume is by the concentration of ions in the blood. When solutions with higher than normal concentrations of ions are infused into kidneys, a dilation of the renal arteries occurs (there is a decrease in renal vascular resistance). In addition, the kidney produces renin, a hormone that, among other actions, initiates a cascade of events to change vascular resistance by constricting or dilating arteries. Thus, the kidneys help control blood pressure both by regulating the amount of fluid in the vascular system and by direct action on the resistance of arteries. Because blood pressure is so highly regulated, it is reasonable to hypothesize that these two ways of regulating blood pressure interact. To study this potential interaction, Wilcox and Peart † wanted to see if the change in renal vascular resistance caused by infusing fluids with high concentrations of ions was related to the production of renin by the kidneys. To do this, they studied the effect of infusions of four solutions of different ion concentration on renal vascular resistance and made simultaneous measurements of renin production by the kidney. Using the raw data in Table D-4, Appendix D, the mean (±SD) changes in renal vascular resistance and renin in four groups are

A. Do these mean values indicate a significant relationship between the changes in renal resistance and the change in renin production? Include a plot in your analysis. B. Using the raw data in Table D-4, Appendix D, evaluate the relationship between the changes in renal resistance and renin, including a plot of the data. C. What features of the regression analysis changed when you used all the data compared to when you used the mean values? Did your overall conclusion change? Why or why not? D. Which one of these two analyses is incorrect, and why?

Table D-4