Photoreaction cycles of acidified bacteriorhodopsin (bRacid 605) at room temperature was studied by nanosecond and picosecond spectroscopy. A precursor of bathobacteriorhodopsin was found to be converted to bathobacteriorhodopsin within 30 ps. Spectra and formation times of batho‐ and lumibacteriorhodopsin are identical to those of bacteriorhodopsin in neutral suspension. However, lumibacteriorhodopsin lifetime is > 700 μs and the formation of metabacteriorhodopsin was not observed in low pH suspension. Thus, the decay process of lumibacteriorhodopsin plays an important role in the proton pump action.

SUMMARY The interrelationship of blood pressure, cardiac output, and peripheral resistance was studied in Dahl "S" and "R" rats after 3 days on a high (8%) NaCl diet. Both "S" and "R" rats were nonnotensive when fed a normal (0.3%) NaCl diet. After 3 days of the high NaCl diet, the "R" rats remained normotensiTe (BP 112 mm Hg), while the "S" rats had an elevation of arterial pressure (BP 133 mm Hg) (p < 0.001). The cardiac outputs of both "S" and "R" rats were similar on the low NaCl diet. After 3 days of high NaCl feeding, the cardiac output of the "R" rats rose 18% above the "R" control level (p < 0.0001), while the peripheral resistance declined 14% below the "R" control level (p < 0.005), and the blood pressure (BP) did not change, a pattern quite contrary to the concept of "whole-body" autoregulation. With a similar 3-day high NaCl feeding in "S" rats, cardiac output (p < 0.005) and peripheral resistance (p < 0.05) both increased 10%, while BP rose 20%. After 7 days of high NaCl feeding, the cardiac output of the "S" rats had returned to normal, while blood pressure and peripheral resistance both continued to be elevated. This pattern of response in "S" rats could be compatible with the concept of "whole-body" autoregulation. However, since both NaCl hypertension and Goldblatt hypertension can occur in settings in which "whole-body" autoregulation appears not be to causally related, one cannot be certain whether "whole-body" autoregulation is playing a causal role in the mechanism of NaCl-induced hypertension in "S" rats. It is a striking dichotomy that 3 days of high salt feeding produces vasoconstriction in "S" rats and vasodilation in "R" rats. (Hypertension 1: 3-7, 1979) KEY WORDS • cardiac output • salt hypertension • blood pressure • diet peripheral resistance • "whole-body" autoregulation

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SUMMARY The effect of high salt intake on rascular and renomedullary prostaglandin (PG) synthesis was compared in Sprague-Dawley and salt-sensitive (S) and -resistant (R) Dahl rats. Animals were given a diet containing either 0.6% or 8% NaCI starting at 5 weeks of age, and were sacrificed 6 weeks later. Systolic blood pressure of S rats increased to 220 ± 7 mm Hg but was unaffected in R and Sprague-Dawley rats. Prostaglandin synthesis was studied in aortic rings and renomedullary mlcrosomes using 14 C-arachidonate as substrate.[*H]PGE, degradation was measured in the renocortical cytosol.In Sprague-Dawley and R rats, aortic PGI t synthesis was not affected by high salt intake, while a significant increase compared to animals on 0.6% NaCI (from 608 ± 84 to 992 ± 108 pmoles/60 min, p < 0.05) was noted in S rats. Enhancement of PGI| synthesis in S rats may be secondary to the hypertension.Salt-loading consistently stimulated renomedullary PGE, synthesis in all three animal groups. S rats, however, had the lowest PG synthesis in renal medullas compared to Sprague-Dawley and R rats when placed on either diet. Thus, even after 6 weeks on high salt, S rats did not reach the levels of PGE, synthesis seen in R or Sprague-Dawley rats on regular diet.The activity of cortical 15-hydroxyprostaglandin dehydrogenase was increased by salt-loading in S and Sprague-Dawley, but not in R rats. R rats had lower dehydrogenase activity than the other two groups when placed on either diet.The observed differences in PG synthesis and catabolism will tend to maintain the net output of renal PGs highest in R and lowest in S rats. These differences correlate with the reported differences in renal papillary flow between these two rat strains and may be relevant to their susceptibility or resistance to hypertension in response to salt. Prostaglandins are involved in the • regulation of physiological and biochemical pathways through both sodium balance and vascular smooth muscle which genetic factors exert their influence on blood tone. It is possible that differences in the pattern of pressure (BP) are unclear. Because of the pivotal role renal and vascular prostaglandin metabolism mediate, of the kidney in regulating BP by maintaining sodium in part, the variable response of BP to salt. The study of the role of prostaglandins in salt-induced hypertension has been facilitated by the development of two From the Department of Pathology, Veterans Administration strains of rats, one sensitive (S) and one resistant (R)%S ^JX^$^ffi?^s£% t0 the effects of salt.-Induction of hypertension in S of Medicine, Minneapolis, Minnesota, and the Broolchaven r a t S by a high salt diet is associated with decreased National Laboratories, Upton, New York renal papillary flow, 10 decreased natriuretic capacity,' Supported in part by grants from the American Heart Assocmand increased systemic vascular resistance 7 compared tion, Minnesota Affiliate, and the Veterans Administration t Q R r a t s T h e p r e s e n t stu( Jy explores the possibility P a S S a -S l S...

SUMMARY The relationship between arterial pressure and left ventricular (LV) functional capacity and LV mass during the natural development of cardiac hypertrophy was assessed in Dahlresistant (R) and -sensitive (S) hypertensive rats maintained on three dietary NaCI regimens (0.4%, 4.0%, and 8.0% for 9 weeks, then 4.0%) from 5 until 20 weeks of age. In R rats, arterial pressure and LV mass were unaffected by diet. In contrast, S rats demonstrated levels of arterial pressure and LV hypertrophy that were graded according to dietary NaCI. Hemodynamic studies on rats under ether anesthesia demonstrated that the graded pressure elevation in S rats was produced by corresponding increases in total peripheral resistance, as cardiac output did not vary. During acute volume loading, the S rats on all diets achieved the same maximum stroke volume as did R rats, despite the marked increase in the arterial pressure of S rats. An analysis of the ejection fraction/after load relationship demonstrated preserved contractile state. The ability of the left ventricle to generate pressure was increased in S rats in direct proportion to the degree of LV hypertrophy. Thus, in young adult S rats, cardiac performance was well compensated since pump and contractile functions were maintained and pressure-generating capacity was increased in relation to the degree of LV hypertrophy. tensive rats is a complex interaction between genetic and environmental factors. 1 Although Dahl salt-sensitive (S) and salt-resistant (R) rats have been observed to have arterial pressure responses to a variety of environmental factors that are quantitatively different, these groups were originally selected and named for their respective pressor responses to alterations in dietary sodium.2 -3 While the arterial pressure level of the R rats is unperturbed even by large increases in dietary sodium, the S rats demonstrate a graded elevation of arterial pressure that is dependent on the sodium intake.4 Therefore, this study was undertaken to evaluate the cardiac responses to varying degrees of hypertension in Dahl R and S rats maintained on different salt diets and to determine whether left ventricular (LV) mass and functional capacity are related to the level of systemic hypertension. Methods Female Dahl R and S rats were obtained from the Brookhaven National Laboratories colony and were placed on either a 0.4%, 4.0%, or 8.0% NaCI diet (g NaCI/100 of food) at 5 weeks of age. The potassium content of all diets was 1.1 g/100 g of food. Since several early deaths were noted in the S rats on the 8% diet, the protocol was modified so that all of the R and S rats initially placed on the 8% diet for 8 to 10 weeks were then switched to the 4% diet. During the 36 hours of transit from Brookhaven to Boston, all rats were fed the 0.4% NaCI diet and had access to water. Except for the stipulated diets, all rats were housed under identical conditions. The dietary regimens of 0.4%, 4.0%, and 8%-to-4% NaCI have been termed low, moderate, and high, respectively.Systolic arterial...