Decreased levels of prostaglandins I2 and E2 in acute gastric mucosal lesions induced by hypoxia

We have observed that the contents of prostaglandin (PG) D2 and 6-keto-PGF1 alpha were five times higher than those of PGE2 and PGF2 alpha in rat gastric mucosa. In order to elucidate the role of PGs in the function of gastric mucosa, we studied the effect of hypoxia on the levels of PGs in relation to the degree of gastric mucosal lesions. 6-Keto-PGF1 alpha levels were significantly decreased only by severe and long-term hypoxia (10% O2, 18 hours) when severe ulcerative lesions were observed. PGE2 levels were significantly decreased even by mild and short-term hypoxia (13% O2, 4 hours) when slight ulcerative lesions were observed. PGF2 alpha and PGD2 levels were significantly decreased by mild and short-term hypoxia; however, there was no significant difference from the control group under severe and long-term hypoxia. These results suggest that each of the PGs plays a different role in the pathogenesis of acute gastric mucosal lesions induced by hypoxia.     

Quantitative determination of prostaglandin levels in human gastric mucosa--analysis by microcolumn high performance liquid chromatography with laser induced fluorescence detection

This study was designed to analyze PGs in human gastric mucosa using biopsy specimens at femtomole level by the combination of microcolumn HPLC and He/Cd laser induced fluorescence detection. Biopsy specimens were taken along the greater curvature at the corpus of the stomach, in which no gastric disease was revealed by endoscopic examination. PGs extracted from human gastric mucosa were derivatized with ADAM, and ADAM-derivatized PGs were injected into the column for analysis. The mobile phase of acetonitrile-water (73:27) containing 0.01% of phosphoric acid was used at a constant pressure of 20 kgf/cm2. Using this system, PGs in few mg of human gastric mucosa obtained by biopsy were well separated and detected; i.e., 1653 +/- 254 (femtomole/mg tissue), 279 +/- 56, 729 +/- 153, 831 +/- 199 for 6-keto-PGF1 alpha, PGF2 alpha, PGE2, and PGD2, respectively. In conclusion, the microcolumn HPLC system with laser induced fluorescence detection is a reliable method for determining individual PGs in human gastric mucosa. In addition, PGI2 is the predominant PG in human gastric mucosa and probably plays an important role in gastric function.     

Mast cells in the rat gastric mucosa are not primarily responsible for PGD2 generation

The present study investigates the contribution of gastric mast cells on PGD2 generation in rat gastric mucosa. Cold-restraint induced stress or i.v. carbachol injection methods were used for gastric mast cell degranulation. In 19 stressed, 15 carbachol-infused and 14 control rats, gastric mast cell counts and gastric mucosa PGD2 assay were performed. Gastric mucosal content of PGF2 alpha was also determined in carbachol infused and control rats. The mean number of gastric mast cells was significantly lower in stressed and carbachol infused than in control rats. Despite these differences in gastric mast cell counts, neither PGD2 or PGF2 alpha contents in the gastric mucosa were significantly different in mast cells degranulated rats than in control animals. These results suggest another source of PGD2 in the rat gastric mucosa other than mast cells.     

Role of COX-1 and COX-2 on skin PGs biosynthesis by mechanical scratching in mice

We examined the involvement of cyclooxygenase (COX)-1 and COX-2 on mechanical scratching-induced prostaglandins (PGs) production in the skin of mice. The dorsal regions of mice were scratched using a stainless brush. COXs expressions in the skin were analyzed using real-time PCR and Western blotting. The effect of acetylsalicylic acid (ASA) on the ability of PGs production were determined based on skin PGs level induced by arachidonic acid (AA) application. Mechanical scratching increased PGD2, PGE2, PGI2 and PGF(2 alpha). COX-1 was constitutively expressed and COX-2 expression was enhanced by scratching. Intravenous administration of ASA inhibited PGs biosynthesis in the normal skin. PGs levels of the skin 6h after ASA administration (ASA 6 h) were almost equal to those of the skin 10 min after ASA administration (ASA 10 min). In the scratched skin, AA-induced PGE2 and PGI2 of ASA 6 h were significantly higher than those of ASA 10 min. The skin PGD2 and PGF(2 alpha) of ASA 10 min were almost same to those of ASA 6 h. In the normal skin of COX-1-deficient mice, skin PGD2 level was lower than that of wild-type mice, although PGE2, PGI2 and PGF(2 alpha) levels were almost equal to those of wild type. In the scratched skin of COX-1-deficient mice, PGD2, PGE2, PGI2 and PGF(2 alpha) levels were lower than those of wild-type mice. These results suggested that cutaneous PGD2 could be mainly produced by COX-1, and PGE2 and PGI2 could be produced by COX-1 and COX-2, respectively, in mice.     

Gastric mucosal formation of prostanoids and the effects of drugs

Prostanoids can be formed throughout the gastrointestinal tract, and qualitative gas chromatography--mass spectrometry has shown that human gastric mucosa can produce PGD2, PGE2, PGF2 alpha 6 keto-PGF1 alpha, thromboxane A2 and lipoxygenase material. Quantitative gas chromatography--mass spectrometry has shown that human gastric mucosa homogenized in Krebs' solution yields mainly 6-keto-PGF1 alpha, with smaller amounts of PGD2 PGE2 and PGF2 alpha. However, the sources of these products and their roles in the gastric mucosa have not been fully elucidated. Recent research from other laboratories indicates that thromboxane formation may be important in gastric ulceration. Our studies with rats in vivo have detected no significant effect of carbenoxolone or deglycyrrhized liquorice on the content of radio-immunoassayable PGE, 6-keto-PGF1 alpha and TXB2 extracted from rat gastric corpus mucosa. The anti-ulcer effect of these drugs in rats therefore does not seem to involve prostanoids.     

Effect of acute surgical vagotomy on the mucosal content of 6-keto-PGF1 alpha, PGE2 and glutathione after intragastric 96% ethanol treatment in rats.

It has been observed earlier that gastric cytoprotection produced by PGI2, beta-carotene, small doses of atropine or cimetidine has failed in surgically vagotomized rats. This phenomenon may be in connection with endogenous prostaglandins (PGs) and glutathione (GSH) level of the gastric mucosa. The aims of the study were to evaluate the effect of vagus nerve on the gastric mucosal 6-keto-PGF1 alpha, PGE2 and glutathione after intragastric 96% ethanol (ETOH) treatment. The observations were carried out on CFY rats. The gastric mucosal damage was produced by intragastric administration of 1 ml 96% ETOH. Acute bilateral surgical vagotomy (ASV) was carried out 30 min prior to ETOH application. The animals were sacrificed 1, 5, 15 or 60 min after ETOH installation. The number and the severity of gastric mucosal lesions were noted and 6-keto-PGF1 alpha, PGE2 an GSH contents of gastric mucosa were measured. It has been found that: 1. the number and the severity of gastric mucosal lesions were increased after ASV compared to those with intact vagal nerve, 2. 96% ETOH treatment increased both the gastric mucosal PGs and GSH levels, 3. 6-keto-PGF1 alpha peaked at 5 min PGE2 and GSH peaked at 15 min after ETOH treatment, 4. ASV decreased the gastric mucosal PGs content and delayed the peaks of PGE2 and GSH. It has been concluded that the decreased content of PGs and the delayed GSH increase may play a pathological role in the failure of gastric cytoprotection of rats after ASV.     

The influence of xanthines on the contractile responses of PGF2 alpha and PGD2 in human parenchymal strips

Prostaglandins (PGs) F2 alpha and D2 are bronchoconstrictor agents which are released under allergic conditions such as asthma. The efficacy and potency of PGF2 alpha and PGD2 differ in some tissues. We compared the effects of these two PGs in sensitized human parenchymal strips. In six experiments, PGF2 alpha 0.1 and 0.3 microM produced greater contractions than PGD2 at the same concentrations. There were no significant differences between the contractions from the two PGs at concentrations of 0.01, 0.03, 1.0-10 microM and the two PGs appeared to be equipotent. We studied the effects of the anti-asthmatic drug theophylline, and its analogue enprofylline, on the contraction caused by these PGs. Theophylline 100 microM caused no change to the cumulative concentration response curves. However, enprofylline 100 microM reduced the PGF2 alpha-induced contractions.     

Late-Phase Accumulation of Inositol Phosphates Stimulated by Prostaglandins D2 and F2α in Neuroblastoma × Glioma Hybrid NG108-15 Cells

The accumulation of inositol phosphates (IPs) in response to prostaglandins (PGs) was studied in NG108-15 cells preincubated with myo-[3H]inositol. As a positive control, bradykinin caused accumulation of IPs transiently at an early phase (within 1 min) and continuously during a late phase (15-60 min) of incubation in the cells. PGD2 and PGF2 alpha did not significantly cause the accumulation of IPs at an early phase but significantly stimulated inositol bisphosphate (IP2) and inositol monophosphate (IP) formation at late phase of incubation. The maximum stimulation was obtained at greater than 10(-7) M concentrations of these PGs, the levels being three-and twofold for IP2 and IP1, respectively. 9 alpha, 11 beta-PGF2 has a slight effect but PGE2 and the metabolites of PGD2 and PGF2 alpha have no effect up to 10(-6)M. The effects of PGD2 and PGF2 alpha were not additive, but the effect of each PG was additive to that of bradykinin at a late phase of incubation. Inositol 1-monophosphate was mainly identified in the stimulation by 10(-5) M PGD2 and 10(-5) M PGF2 alpha, whereas both inositol 1-monophosphate and inositol 4-monophosphate were produced in the stimulation by 10(5) M bradykinin. Depletion of extracellular Ca2+ diminished the stimulatory effect of PGD2 and PGF2 alpha and late-phase effect of bradykinin, but simple Ca2+ influx into the cells by high K+, ionomycin, or A23187 failed to cause such late-phase effects. These results suggest that PGD2 and PGF2 alpha specifically stimulate hydrolysis of inositol phospholipids.     

Modulation of 3H-prostaglandin E2 binding sites in the rabbit gastric mucosa

The binding of 3H-prostaglandin E2 (PGE2) to rabbit gastric mucosa was investigated. Binding depended on incubation time, temperature and pH, and was saturable and reversible. Scatchard plot analysis revealed a single class of binding sites with a dissociation constant (Kd) of 5.33 +/- 0.21 nM and a maximum number of binding sites (Bmax) of 138.1 +/- 3.4 fmol/mg protein. PGE1 and 16,16-dimethyl PGE2 potently competed with 3H-PGE2 for the binding sites of gastric mucosa, whereas PGA2, PGF2 alpha, 6-keto PGF1 alpha and thromboxane B2 were less potent. The gastric mucosa prepared from the rabbits given indomethacin (5 mg/kg s.c. three times) showed a lower Kd (2.47 +/- 0.19 nM) for 3H-PGE2 than that from untreated one. Treatment with a PGE1 analog, misoprostol (320 micrograms/kg s.c. three times) lowered the Bmax to 74.1 +/- 2.4 fmol/mg protein without any significant effect on the Kd value. It is concluded that rabbit gastric mucosa has specific binding sites for 3H-PGE2 which may be modulated by the levels of PGs in vivo.     

Determination of prostaglandin F2 alpha, E2, D2 and 6-keto-F1 alpha in human cerebrospinal fluid.

Prostaglandin (PG)F2 alpha, E2, D2 and 6-keto-F1 ALha were determined in human cerebrospinal fluid by a mass spectrometric technique. The samples were obtained from 12 patients with suspected intracranial disease. A 64 fold variation in PG levels was observed. The major PG was 6-keto-F1 alpha (0.12--15 ng/ml). PGF2 alpha and PGE2 were present in lower concentrations PGD2 was below the level of detection (0.05 ng/ml) except in one patient with extremely high total levels of PGs.     

Intraluteal infusions of prostaglandins of the E, D, I, and A series prevent PGF2 alpha-induced, but not spontaneous, luteal regression in rhesus monkeys

A luteotropic role for prostaglandins (PGs) during the luteal phase of the menstrual cycle of rhesus monkeys was suggested by the observation that intraluteal infusion of a PG synthesis inhibitor caused premature luteolysis. This study was designed to identify PGs that promote luteal function in primates. First, the effects of various PGs on progesterone (P) production by macaque luteal cells were examined in vitro. Collagenase-dispersed luteal cells from midluteal phase of the menstrual cycle (Day 6-7 after the estimated surge of LH, n = 3) were incubated with 0-5,000 ng/ml PGE2, PGD, 6 beta PGI1 (a stable analogue of PGI2), PGA2, or PGF2 alpha alone or with hCG (100 ng/ml). PGE2, PGD2, and 6 beta PGI1 alone stimulated (p less than 0.05) P production to a similar extent (2- to 3-fold over basal) as hCG alone, whereas PGA2 and PGF2 alpha alone had no effect on P production. Stimulation (p less than 0.05) of P synthesis by PGE2, PGD2, and 6 beta PGI1 in combination with hCG was similar to that of hCG alone. Whereas PGA2 inhibited gonadotropin-induced P production (p less than 0.05), that in the presence of PGF2 alpha plus hCG tended (p = 0.05) to remain elevated. Second, the effects of various PGs on P production during chronic infusion into the CL were studied in vivo. Saline with or without 0.1% BSA (n = 12), PGE2 (300 ng/h; n = 4), PGD2 (300 ng/h; n = 4), 6 beta PGI1 (500 ng/h; n = 3), PGA2 (300 ng/h; n = 4), or PGF2 alpha (10 ng/h; n = 8) was infused via osmotic minipump beginning at midluteal phase (Days 5-8 after the estimated LH surge) until menses. In addition, the same dose of PGE, PGD, PGI, or PGA was infused in combination with PGF2 alpha (n = 3-4/group) for 7 days. P levels over 5 days preceding treatment were not different among groups. In 5 of 8 monkeys receiving PGF2 alpha alone, P declined to less than 0.5 ng/ml within 72 h after initiation of infusion and was lower (p less than 0.05) than controls. The length of the luteal phase in PGF2 alpha-infused monkeys was shortened (12.3 +/- 0.9 days; mean +/- SEM, n = 8; p less than 0.05) compared to controls (15.8 +/- 0.5). Intraluteal infusion of PGE, PGD, PGI, or PGA alone did not affect patterns of circulating P or luteal phase length.(ABSTRACT TRUNCATED AT 400 WORDS)     

Characterization of gastric mucosal prostaglandin E2 receptor

1. The binding characteristics of gastric mucosal prostaglandin (PG) E2 (PGE2) receptor were investigated using mucosal cell membranes from rat stomach. The binding was found to be dependent upon PGE2 and membrane protein concentration, the time of incubation and the pH of the mixture, being highest at pH 3.0. 2. Scatchard analysis of the binding data revealed a curvilinear plot with high affinity binding (Kd = 2 nM; Bmax = 0.106 pmol/mg protein) and low affinity binding (Kd = 319 nM; Bmax = 2.262 pmol/mg protein) sites. 3. Competitive displacement study indicated that the receptor was specific for PGs of the E series, as PGF2 alpha and 6-keto-PGF1 alpha failed to displace the PGE2. 4. The study is the first report to provide biochemical parameters of specific PGE receptors in rat gastric mucosa.     

Effective use of rabbit gastric antral mucosal slices in prostaglandin synthesis and metabolism studies

Intact slice preparations of rabbit stomach (antral mucosa, corporal mucosa, antral muscle and corporal muscle) were incubated and the released prostaglandins (PGs) were measured by reverse-phase high-performance liquid chromatography using 9-anthryldiazomethane for derivatization. With respect to total PG production, the highest amounts were generated by antral mucosal slices. Antral mucosal slices produced PGE2, 6-keto PGF1 alpha, thromboxane B2, PGF2 alpha and PGD2 (in descending order of magnitude) and possessed a high capacity for producing 13,14-dihydro-15-keto derivatives of both PGE2 and PGF2 alpha. Studies utilizing aspirin, EGTA or Ca2+ revealed that PG release by antral mucosal slices in the present in vitro system reflects a composite of the activities of phospholipase A3, PG cyclooxygenase and PG-metabolizing enzymes. These results show that antral mucosal slices will be useful in physiological and pharmacological studies on PG synthesis and metabolism of the stomach.     

Regional and species differences in endogenous prostaglandin biosynthesis by brain homogenates.

Endogenously formed prostaglandins (PGs) D2, E2 and F2 alpha were determined in homogenates of brain regions from rat, guinea-pig, rabbit and cat, using gas-chromatography-mass spectrometry. The main PGs formed in the brain regions of the rat were PGD2, in the guinea-pig PGD2 and PGF2 alpha, in the rabbit PGF2 alpha and in the cat PGE2. Brain regions from the same animal species showed the same pattern of PG formation. They varied, however, in the amount of total PGs formed, the limbic system and the cerebral cortex being highest and cerebellum lowest.     

Putative mechanism of the itch-scratch circle: repeated scratching decreases the cutaneous level of prostaglandin D2, a mediator that inhibits itching

In atopic dermatitis, scratching of the skin as a reaction to itching causes injury to the skin, which, in turn, further increases the itching resulting in the establishment of the so-called itch-scratch circle. We have shown that prostaglandin (PG) D2 plays an inhibitory role against pruritus in mice with atopic-like dermatitis; therefore, we examined the relationship between scratching and the cutaneous PGD2 level using an artificial scratching model with a wire brush. Mechanical scratching induced a temporary increase of the skin PGs levels (PGE2, PGD2, 6-ketoPGF1alpha, PGF2alpha). The skin PGD2 level and the ability of PGD2 production decreased at 48 h after repeated scratch, compared to that of normal skin, not so after single scratch. Immunohistochemical analysis and Western blotting revealed a decrease in the levels of cyclooxygenase-1 (COX-1) and hematopoietic PGD synthase in mechanically scratched skin. The reduced ability of the skin for PGD2 production following mechanical scratching could be caused by this decrease in the expression levels of COX-1 and PGD2 synthase. The results suggest that repeated scratching in mice decreases the ability of the skin to produce PGD2, which is an endogenous mediator that inhibits pruritus, resulting in the establishment of the itch-scratch circle.     

Characterization of prostaglandin (PG)-binding sites expressed on human basophils. Evidence for a prostaglandin E1, I2, and a D2 receptor.

Recent data suggest that prostaglandins (PGs) are involved in the regulation of basophil activation. The aim of this study was to characterize the basophil PG-binding sites by means of radioreceptor assays using 3H-labeled PGs. Scatchard analysis for pure (greater than 95%) chronic myeloid leukemia (CML) basophils revealed two classes of PGE1-binding sites differing in their affinity for the natural ligand (Bmax1 = 217 +/- 65 fmol/10(8) cells; Kd1 = 0.5 +/- 0.2 nM; Bmax2 = 2462 +/- 381 fmol/10(8) cells; Kd2 = 47 +/- 20 nM; IC50 = PGE1 less than PGI2 less than PGD2 less than PGE2 less than PGF2 alpha) as well as two classes of PGI2 (iloprost)-binding sites (Bmax1 = 324 +/- 145 fmol/10(8) cells; Kd1 = 0.5 +/- 0.3 nM; Bmax2 = 2541 +/- 381; Kd2 = 27 +/- 6 nM; IC50 = PGI2 less than PGE1 less than PGD2 less than PGE2 less than PGF2 alpha. In addition, CML basophils exhibited a single class of PGD2-binding sites (Bmax = 378 +/- 98 fmol/10(8) cells; Kd = 13 +/- 4 nM; IC50: PGD2 less than PGI2 less than PGE1 less than PGE2 less than PGF2 alpha). In contrast, we were unable to detect specific saturable PGE2-binding sites. Primary and immortalized (KU812) CML basophils revealed an identical pattern of PG receptor expression. Basophils (KU812) expressed significantly (p less than 0.001) lower number of PGE1 (PGI2)-binding sites (Bmax1: 9% (20%) of control; Bmax2: 36% (50%) of control) when cultured with recombinant interleukin 3 (rhIL-3), a basophil-activating cytokine, whereas rhIL-2 had no effect on PG receptor expression. Functional significance of binding of PGs to basophils was provided by the demonstration of a dose-dependent increase in cellular cAMP upon agonist activation, with PGE1 (ED50 = 1.7 +/- 1.1 nM) and PGI2 (ED50 = 2.8 +/- 2.3 nM) being the most potent compounds. These findings suggest that human basophils express specific receptors for PGE1, PGI2 as well as for PGD2.     

Prostaglandin synthesis and catabolism in the gastric mucosa: studies in normal rabbits and rabbits immunized with prostaglandin E2

Antral and fundic mucosal homogenates obtained from prostaglandin E2-immunized rabbits converted 14C-arachidonic acid to prostaglandin E2, 6-keto prostaglandin F1 alpha, prostaglandin F2 alpha, and prostaglandin D2. Percentage conversion of 14C-arachidonic acid to these prostaglandin products was not significantly different in prostaglandin E2-immunized rabbits compared with control rabbits (thyroglobulin-immunized and unimmunized rabbits combined). Synthesis of 6-keto prostaglandin F1 alpha, prostaglandin E2 and 13,14-dihydro 15-keto prostaglandin E2 from endogenous arachidonic acid after vortex mixing fundic mucosal homogenates was similar in prostaglandin E2 immunized rabbits and control rabbits. Both in prostaglandin E2-immunized rabbits and controls, 3H-prostaglandin E2 was catabolized extensively by the fundic mucosa, whereas 3H-6-keto prostaglandin F1 alpha, 3H-prostaglandin F2 alpha, and 3H-prostaglandin D2 were not catabolized to any appreciable extent. The rate of catabolism of PGs was not significantly different in prostaglandin E2-immunized rabbits and control rabbits, with the exception of prostaglandin F2 alpha which was catabolized slightly more rapidly in prostaglandin E2-immunized rabbits. These results indicate that development of gastric ulcers in prostaglandin E2-immunized rabbits is not associated with an alteration in the capacity of the gastric mucosa to synthesize or catabolize prostaglandins.     

Liquid chromatographic-mass spectrometric determination of cyclooxygenase metabolites of arachidonic acid in cultured cells

A liquid chromatographic-electrospray ionization-mass spectrometric (LC-ESI-MS) technique was developed to simultaneously determine the cyclooxygenase metabolites of arachidonic acid (6-keto-PGF(1alpha), PGD(2), PGE(2), PGF(2alpha), and PGJ(2)) produced by cultured cells. Samples were separated on a C(18) column with water-acetonitrile mobile phase, ionized by electrospray, and detected in the positive mode. Selected ion monitoring (SIM) of m/z 353, 335, 335, 319, and 317 were used for quantifying 6-keto-PGF(1alpha), PGD(2), PGE(2), PGF(2alpha), and PGJ(2), respectively. Prostaglandins were detected at concentrations as low as 1 pg (S/N=3) on the column. The method was used to determine the production of PGs from bovine coronary artery endothelial cells (ECs) and human prostate cancer cells (PC-3) with different degree of invasiveness. Bradykinin (10(-6) M) stimulated a marked increase in the production of 6-keto-PGF(1alpha), PGE(2), and PGF(2alpha) and a small increase of PGD(2) by ECs. 6-Keto-PGF(1alpha) was the major metabolite in these cells. The production of PGE(2) was threefold higher and PGD(2) was twofold higher in PC-3-S (invasive) cells than in PC-3-U (non-invasive) cells.     

Age-associated decreases in prostaglandin contents in human gastric mucosa.

This study was designed to clarify effects of ageing on human gastric mucosal prostaglandin (PG) contents. Forty examinees were divided into 5 age groups of 8 persons each, as follows: age under 40, age 40-49, age 50-59, age 60-69, and age over 70. PG contents in human gastric mucosa were measured by microcolumn high performance liquid chromatography (HPLC) with helium/cadmium laser induced fluorescence detection using biopsy samples obtained by endoscopy. The contents of 6-keto-PGF1 alpha, PGF2 alpha, PGE2, and PGD2 in the under 40 group were 638 +/- 39, 97 +/- 16, 468 +/- 68, 497 +/- 86 (pg/mg tissue), respectively. No significant differences in PG contents among groups aged under 70 were observed. In contrast, significantly low PG contents in the over 70 group were observed, i.e., the contents of 6-keto-PGF1 alpha, PGF2 alpha, PGE2, and PGD2 were 311 +/- 58, 36 +/- 8, 196 +/- 48, 171 +/- 40, respectively, and their contents were significantly lower than those in other age groups. In conclusion, gastric mucosal PG contents decrease significantly in over 70 years-old and this might be a contributing factor in the pathogenesis of gastric ulcers in elderly people.     

Effect of prostaglandins on cyclic nucleotide levels in cultured keratinocytes.

Ginea pig ear epidermal cells (keratinocytes) were established in primary cultures using trypsin, and treated in their proliferative phase of growth with prostaglandins E1, D1, F1 alpha, E2, D2, or F2 alpha. This phase is induced by the addition of retinoic acid during cell plating. Intracellular content of cAMP and cGMP was measured by radioimmunoassay at various times after treatment. Maximum stimulation of cAMP levels was observed with PGD2, smaller increases with PGE2 and relatively transient rises with PGF2 alpha which were of low significance, but confirm earlier data. Similar results were observed with PGD1, PGE1, and PGF1 alpha with smaller increases. The effects of D and E PGs were biphasic. Significant increases in cGMP were immediately observed with PGD2 and PGE2. With PGF2 alpha, maximum cGMP levels were noted after some delay. All PGs tested showed some effect in elevating cyclic nucleotides in keratinocytes. The most striking result was the increase in cAMP on PGD2 treatment.