Abstract
Disclosure: F.I. Chasalow: None. Background: Earlier, my laboratory reported 3 novel endogenous steroids (SS) that cross react with digoxin-specific antibodies (DLM). The SS are readily distinguished from all other steroids by 3 characteristics: [1] each is a phosphocholine diester, [2] each has more than 21 carbon atoms in the steroid fragment and [3] the extra carbons form an E-ring with a cyclic lactone. The discovery included a biosynthetic scheme with known enzymes and no need for a ‘magic’ step. Function: NaK-ATPase has 3 subunits, designated FXYD, α, and β. Affinity for Na+ and K+ ions is regulated by FXYD proteins. Each SS matches a tissue-specific α-subunit. Each α-subunit has 2 different binding sites for steroids. One site binds a SS; the ligand of the other site is unknown. For example, Ionotropin is specific for the α subunit present in cardiac and renal tissue. Kaleotropin is isolated from gonads, but the α subunit which matches each specific ovarian cell type is unknown. Galotropin (G-trop): One of the SS, G-trop, was detected as a DLM in human breast cyst fluids, specifically cysts with high K+ ion levels. Solubility properties distinguished it from previously known cardiac glycosides and, like other DLM, it inhibited NaK-ATPase. G-trop was also detected in milk from cows, sheep and goats. Ions derived from Ionotropin (m/z=341 Da) or Kaleotropin (m/z=369 Da) were not present in milk extracts. On LC-MS, G-trop fragmented to an ion at m/z= 381 Da. Trial and error analysis suggests C(25)O(4)H(34). No other formula is consistent with m/z=381 Da. G-trop: G-trop wasn’t present in serum from children. At 22-26 weeks of gestation, whether or not a pregnant woman had pre-eclampsia, serum had low levels of G-trop. Maternal G-trop increases during the 3(rd) trimester, coincidentally with initiation of milk production; simultaneously, K+ ion levels in milk increased. Pre-eclampsia. In a pilot study, 65% of patients (n=20) with pre-eclampsia had elevated levels of Ionotropin precursor and 30% had elevated levels of Kaleotropin precursor. 25% of patients with pre-eclampsia develop life-threatening hypertension or seizures, typical of the expected response to elevated Ionotropin levels. Therapy includes immediate delivery of the infant at 30-36 weeks of gestation. Maternal G-trop synthesis has not yet begun and mother’s milk has low K+ ion levels. Elevated maternal Kaleotropin is not the cause of maternal hypertension, suggesting a specific gestational maternal α-subunit is its target. Kaleotropin from placenta may be the signal to respond to maternal hypokalemia. Necrotizing enterocolitis (NEC):In utero the fetus does not absorb K+ from the GI tract because fetal need for K+ ion is provided via the placenta. Concept: After premature delivery, without G-trop in milk, the infant can’t absorb K+ from the GI tract; the GI tract fails to grow and tight junctions do not form. As a result, infants are at high risk for developing NEC. Presentation Date: Thursday, June 15, 2023